En can't be used as a pronoun to replace people. See if these examples help:

Luc s'occupe de Jean. -- Luc s'occupe de lui. (NOT: Luc s'en occupe.)

Luc s'occupe des fleurs. -- Luc s'en occupe. Luc takes care of the flowers -- Luc takes care of them  

In the last sentence, en replaces des fleurs and "them" refers to an object, not a person. If you were taking of persons, you would need a different construction. 

Luc s'occupe de mes parents. -- Luc s'occupe d'eux. 

Hope that helps. 

If you read my previous post again, I did include an example using "them" referring to flowers. Since flowers aren't people, the use of "en" is OK.

Il s'occupe de ses grand-parents. Il s'occupe d'eux. -- He takes care of them (grand parents)
Il s'occupe des fleurs. Il s'en occupe. -- He takes care of them (the flowers).

i did read your previous post.  your example does not have any relevance to the example in the quizz which didnt specify whether or not ‘en’ was supposed to rever to inanimate objects or humans. It’s the specific quizz question that i am querying.

Thanks, Chris, for your excellent answer to Marnie's question. I was wondering the same thing. It makes sense that "them" can refer to things or people. Your examples were particularly useful for helping me see that. :)