1. He stayed up late studying last night.

Question

1. He stayed up late studying last night.

2. He stayed up late while he was studying last night.

3. He stayed up late while he studied last night.

(Does #1 mean #2 or #3? Do we have to use 'while' or'when', etc?)

Answer 1

1. He stayed up late studying last night.

They are all correct, but 1 is more commonly used.