Read the following sentence, and answer the question below: Why was this person tired today?

Read the following sentence, and answer the question below:

因为明天晚上我没有睡好觉，所以今天我很累。

Why was this person tired today?

a.) It is very late at night

b.) They had a 6am class this morning

c.) They didn't sleep well last night

d.) They aren't tired