John : Why didn’t you attend the class today?
Martin : I was so high with my brother.
John : Oh, I should have known that you were up to something.
What does John mean by saying “I should have known that you were up to something.”?
I should have known that you were doing something wrong.
I should have known that you didn't want to come to the class anyway.
I should have known that you were doing something inappropriate.
I should have known that you were depending on something.