French language Q&A Forum

Sometimes you see India written like Inde (Informations générales sur Inde)

Sometimes you see  with an l' connaissance de l'Inde

How to know when to use l' and when not to? 

In the Weekend Challenge: 'My plan for the day of the exam' one of the translations required is 'that I'll have chosen the day before'. 

The answes given are: 

'que j'aurai choisiS la veille'  OR 'que j'aurai sélectionnéS la veille'

There is no object pronoun in either of these answers, so why are the past participles 'choisi' and 'sélectionné' writen with an S added for agreement?

Thank you