This sentence is intentionally **ambiguous**. The pronoun **"he"** could logically refer to either:

- **The doctor** (he called to say he was running late), or
- **The nurse** (he called because the nurse was late)

This is a classic example of **pronoun ambiguity** or an **anaphora resolution problem**, often used in linguistics and psychology research (sometimes called a "Winograd schema"). Without additional context, you cannot determine with certainty who was late.
