Here's a problem to solve: Which is a hypothesis that can be easily tested?

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

- A: The Moon causes high tides.
 
- B: During which season are the tides the highest?
 
- C: What is the phase of the Moon when tides are highest?
 
- D: When the Moon is full, the tides will be at their highest.
 