Question

Use a semi-modal verb to complete the sentence.

I _________ wake up at $5$ o'clock in morning when I was a young boy.

Answer 1

Use to + verb is a regular verb and means something that happened but doesn't happen any more. It uses -ed to show past tense. But since it always means something that happened in the past, it should always use past tense. Hence, "used to" is the appropriate semi-modal verb form.