Answer: When the sun rises, it is morning.
Explanation: Numerous sentences can be constructed using the word 'when' including statements and questions. The answer given is a statement. Other examples include;
- When will lunch be ready?
- We can go to the shops when you are ready.
- When will you be free to meet up?
- I enjoy consuming egg fried rice when I am sick.
The word 'when' is used in coordination with timings of events.