The sudden pressure drop will cause a sudden temperature drop.
If there is sufficient moisture in the air, and if the temperature falls below the dew point, it will cause water droplets to precipitate out of the air.
The unstated assumptions in this question are that:
a. There is sufficient moisture in the air.
b. The pressure and temperature drops are sufficiently large.
So the use of the words "will occur" in option C is probably a bit too strong. "May occur" would be more accurate.
But the other options are all wrong, so option C is the best answer.