A person who is afraid of falling asleep usually keep standing. By sitting down, one can easily fall asleep if he is feeling sleepy.
This justifies what answer for what question? Q & A: 
John kept standing up. He was afraid that if he were sitting down he might do something. What might he be afraid of?
Options:
- fall asleep
- being supported on chair
- comfort
- clowns
- flatulence
fall asleep