to increase strength for moving around in the cabin to keep from becoming overweight on a space mission to minimize the loss of muscle mass due to microgravity to ensure that bodily fluids do not tend to collect in the feet
I gave my students this multiple choice question: Which of these is the best reason for exercising on space flights?

Only one answer is correct among these 4 choices:
- to increase strength for moving around in the cabin
- to keep from becoming overweight on a space mission
- to minimize the loss of muscle mass due to microgravity
- to ensure that bodily fluids do not tend to collect in the feet

Could you tell me which one is correct?

to minimize the loss of muscle mass due to microgravity