Whose backgrounds

Please check my answers to the following grammar test.

1. As the report has shown, ____________ shorter words and sentences does not necessarily make a passage easy to read.
( A) writers use (B) in using (C) when suing ( D) using
2. ___________ in part because we respond intentionally to symbols.
( A) Advertising works (B) There is advertising working
( C) It works as advertising ( D) It is advertising that works
3. The factory employee who ___________ absent frequently was notified by his supervisor that he would not have to come to work again.
( A) had been (B) has been (C) had ( D) has
4. Perhaps the best use of color ____________ in the weather maps printed daily in many newspapers.
( A) occurring (B) occurs (C) that occurs ( D) occurred
5. Even if you stay in the United States and Canada, you will work with people _________ backgrounds differ from yours.
( A) with whom (B) in which (C) when ( D) whose

My answers are as written.
1. D
2. D
3. B
4. B
5. D