词汇。

1.My ________ (钥匙) are on the table.

2.—________ (在哪里)is the baseball?

   —I don't know.

3. My backpack is ________ (在……下面) the dresser.

4. Please ________ (带来) your dictionary to school tomorrow.

5. The boy is ________ (在两者之间) Betty and Kate.

一束光线垂直入射到平面镜上，反射角为______；若一束光线的反射光线与界面成30°，则反射光线与入射光线的夹角为______。