听力原文：

G: Hey, Bob! I didn't see you last weekend. How was your weekend?

B: I was quite busy. I stayed at home all the time.

G: Why?

B: I studied for a test.  

G: Not much fun.

B: It was too bad, but I had to do it!

Question: Why did Bob stay at home on the weekend?

参考答案：

Because he studied for a test.