Out of all the pronouns, "whom" makes the most sense grammatically. This allows us to narrow it down to A or D.
In order for it to be the object of a preposition, there would have to be a preposition in front of it. "For," however is <em>not</em> a preposition. In fact, there isn't a preposition in the whole question.
This leaves us with option D, which is the correct answer.
You can better tell it's a direct object if you flip the sentence around a bit.
Your sister is waiting <em>for whom</em>?
"Whom" is essentially receiving the action. "Whom" is what your sister is waiting for.
Answer: D. whom; direct object.
B.
Not A. because it isn't only for solving simple problems.
Not C. because it CAN work well with personal or school problems.
Not D. because you can't solve a problem before their is a problem.
I hope this helped.
Because people are fake, rude, two-faced, and toxic. It's a place where people can get a chance to get their feelings out to a perosn behind the screen because they think they can get away with it. It's sickening.
Answer:Why do Jessie Prescott and her parents eat macaroni and chesse so often.
Explanation: