Grammatical query

Question

Good morning,My answer to Q7 in this test was wrong.I wrote 'montre' instead of 'montres'.I am not sure why an 's' has been added to 'montre' since the auxiliary verb is avoir and not etre.(I cannot add the accents).I can only assume I've missed a lesson where this is discussed but I suspect it has something to do with the use of 'leur'.Thank you for your help.Keith

Accepted Answer

The attached lesson likely covers the information you are missing on the special case of agreement of past participle in passe' composé with auxiliary avoir - it depends on direct object preceding avoir, not the indirect object. eg 'We gave them to them' =  «Nous les leur avons donnés»  That is avoir still 'agrees' with nous and 'donnés' agrees with les (not leur).
https://french.kwiziq.com/revision/grammar/special-cases-when-the-past-participle-agrees-in-number-and-gender-when-used-with-avoir-in-le-passe-compose-conversational-past

Answer

Thank you.Your explanation has helped me to understand it now.