1. With the auxiliary TO HAVE, we look for the DO. The DO is found by asking the question QUOI? after the verb. J'ai offert QUOI? Des billets. The DO is placed after the verb, then, NO agreement takes place.

2. With the auxiliary TO BE, we look for the subject. The subject is found by asking the question QUI? or QUI EST-CE QUI? before the verb. Qui est entré au Temple de la Renommée? Ces deux athlètes. The past participle must agree in gender and number with ATHLÈTES (Masc. Plur.) = entrés. 

3. With the auxiliary TO HAVE, we look for the DO. The DO is found by asking the question QUOI? or QUI? after the verb. Ma mère a téléphoné QUI? NO answer is given to that question since the verb TÉLÉPHONER takes an indirect object (On téléphone À quelqu'un), then, no agreement takes place. 

4. With the auxiliary TO BE, we look for the subject. The subject is found by asking the question QUI? or QUI EST-CE QUI? before the verb. Qui est allé faire des courses? Mes amies. The past participle must agree in gender and number with AMIES (Fém. Plur.) = allées.

5. With the auxiliary TO HAVE, we look for the DO. The DO is found by asking the question QUOI? after the verb. Vous avez visité QUOI? Les châteaux. The DO is placed after the verb, then, NO agreement takes place. 

6. With the auxiliary TO BE, we look for the subject. The subject is found by asking the question QUI? or QUI EST-CE QUI? before the verb. Qui est descendu de l'avion? Ils. The past participle must agree in gender and number with ILS (Masc.Plur.) = descendus.

7. We have a reflexive verb here, so we have to find if the reflexive pronoun (se) is the DO. To do this we change the TO BE auxiliary into the TO HAVE auxiliary and we ask the question QUI? after the verb, A RÉVEILLÉ QUI? the answer to that question is SE which replaces Lorraine. Since the DO is placed before the verb, the past participle must agree in gender and number with LORRAINE (Fém. Sing.) = réveillée.

8. With the auxiliary TO HAVE, we look for the DO. The DO is found by asking the question QUOI? after the verb. J'ai reçu QUOI? QUE, a relative pronoun which replaces Les patins. The DO is placed before the verb, then, the past participle must agree in gender and number with PATINS (Masc. Plur.) = reçus. 

9. We have a reciprocal verb here, so we have to find if the reflexive pronoun (se) is the DO. To do this we change the TO BE auxiliary into the TO HAVE auxiliary and we ask the question QUI? after the verb, ONT MARIÉ QUI? the answer to that question is SE which replaces Ma soeur et son petit ami. Since the DO is placed before the verb, the past participle must agree in gender and number with MA SOEUR ET SON PETIT AMI (Masc. Plur.) = mariés.

10. With the auxiliary TO BE, we look for the subject. The subject is found by asking the question QUI? or QUI EST-CE QUI? before the verb. Qui est resté muet d'admiration? Elles. The past participle must agree in gender and number with ELLES (Fém. Plur.) = restées.

11. We have a reciprocal verb here, so we have to find if the reflexive pronoun (se) is the DO. To do this, we change the TO BE auxiliary into the TO HAVE auxiliary and we ask the question QUI? after the verb, ONT DIT QUI? the answer to that question is not SE given that We say something TO someone. Since 
SE is an indirect pronoun, NO agreement takes place.

12. We have a reciprocal verb here, so we have to find if the reflexive pronoun (se) is the DO. To do this, we change the TO BE auxiliary into the TO HAVE auxiliary and we ask the question QUI? after the verb, ONT ECRIT QUI? the answer to that question is not SE given that We write something TO someone. Since SE is an indirect pronoun, NO agreement takes place.

13. We have a reflexive verb here, so we have to find if the reflexive pronoun (se) is the DO. To do this, we change the TO BE auxiliary into the TO HAVE auxiliary and we ask the question QUI? ou QUOI? after the verb, ONT LAVÉ QUOI? the answer to that question is not SE, but Les mains (une partie du corps) which is placed after the verb.Therefore, NO agreement takes place. 

14. We have a reflexive verb here, so we have to find if the reflexive pronoun (se) is the DO. To do this we change the TO BE auxiliary into the TO HAVE auxiliary and we ask the question QUI? after the verb, A COUCHÉ QUI? the answer to that question is SE which replaces Cette étudiante. Since the DO is placed before the verb, the past participle must agree in gender and number with CETTE ÉTUDIANTE (Fém. Sing.) = couchée.

15. We have a verb conjugated with TO HAVE, so we have to find the DO. To do this we ask the question QUI? after the verb, A OBÉI QUOI? there is NO answer to that question since we obey TO something. Therefore, Règlements is an indirect object, so NO agreement takes place.

16. With the auxiliary TO BE, we look for the subject. The subject is found by asking the question QUI? or QUI EST-CE QUI? before the verb. Qui est revenu? Mon frère et son ami. The past participle must agree in gender and number with MON FRÈRE ET SON AMI (Masc. Plur.) = revenus. 

17. Remember! This is one of the verbs that has an indirect pronoun as Object. 

18. With the auxiliary TO HAVE, we look for the DO. The DO is found by asking the question QUOI? after the verb. Vous avez monté QUOI? L'escalier. The DO is placed after the verb, then, NO agreement takes place. Here is one example of a verb that could be used at times with TO BE and other times with TO HAVE. It is used here with TO HAVE given the presence of a DO. 

19.  With the auxiliary TO HAVE, we look for the DO. The DO is found by asking the question QUOI? after the verb. Vous avez acheté QUOI? EN (pronoun) which replaces Des (partitive article) tomates. Remember there is NO agreement with EN.

20. We have a reciprocal verb here, so we have to find if the reflexive pronoun (se) is the DO. To do this, we change the TO BE auxiliary into the TO HAVE auxiliary and we ask the question QUI? ou QUOI? after the verb, ONT ÉCRIT QUOI? the answer to that question is not SE given that We write something TO someone, but Les lettres which happen in this sentence to be placed before the verb.Therefore, in that specific example, the past participle must agree in gender and number with LETTRES(Fém. Plur.) = écrites.