CALVIN and HOBBES - 

Improve Your Vocab!

I'll bet - in reply to a statement to show that you agree with it or that you expected it to be true, usually when you are annoyed or amused by it. [informal, spoken, feelings]. Synonyms: I agree(d). For example, We are out of power, I'll bet Frank's forgotten to pay the bill.

Stupid - In this case it is foolish, not important, dull, senseless. For example, I forgot to pay that stupid bill! That's why we're out of power.