1. a. 'My favourite fruit is an apple.' b. 'My favourite fruit is apple.' c. 'My favourite fruit are apples.' d. 'My favourite fruit is apples.'
- You don't like an apple in particular. 'My favourite fruit is an apple from Brazil, but I don't know (or don't remember) exactly what apple it is'. Then option a. is out. - 'My favourite fruit' requires a singular verb.