I don't know that ma,nnnnnnnnnnnnnnnnnnnnn
Here, you would need to add the preposition "in."
The sentence should read: My elder sister is really interested in the problems of the environment.
Other prepositions would not make sense and could confuse the reader as to the intended meaning.
I read that book.What do you need help with?
Answer:
eats
Explanation:
does she usually __eats____ a big sandwich?
