E. 1) can 2) can't 3) could 4) couldn't

The correct answer is **2) can't**. In the past, the butterfly was unable to find food. The past of 'can' is 'could', so the past of 'can't' is 'couldn't'. However, the context of the sentence is about the past, so 'couldn't' is the best choice. The correct sentence is 'The butterfly **couldn't** find any food and was hungry all the time.'