Can’t think straight

Do you know the English phrase “can’t think straight“? Look at the conversation below. Can you guess the meaning?

Bill: How is work?

Kevin: So busy. I have so much to do I can’t think straight.

Does it mean

a) be busy

b) be unable to think clearly

c) be unable to think in a straight line

d) be tired

The answer is below! ↓

Answer: b) be unable to think clearly