Here's a problem to solve: Which of these best describes when a lunar eclipse will occur?

Among the 4 following options, which is the correct answer?

- A: when Earth is between the Moon and the Sun
 
- B: when the Moon passes between Earth and the Sun
 
- C: when the Sun is between Earth and the Moon
 
- D: when Earth is at a 90° angle to the Moon and the Sun
 