根据所给中文写出单词的合适形式。

1. The hair clip              ( 配) my new skirt very well.

2. She is so                (激动) when she knows the news.

3. This beautiful walkman             (花费) 300 dollars.

4. The price of the teddy bear is too             (昂贵).

5. This is a              (相当) difficult question.

下列运算正确的是（　　）

A．（a³）²=a⁵

B．（-a）²=a²

C．2a-a=2

D．a³+a²=a⁵