根据句意, 写出括号内所给单词的适当形式。
1. He was rudely refused by the company ________ (simple) because of his ugly appearance.
2. The increase in excellent teachers can lead to the ________ (raise) of standards in schools.
3. The wonderful piece of music is a couple of African ________ (music) work.
4. Bill Gates has been the ________ (wealth) person in the world for quite a few years.