During heavy rainfall and storms, thatched roofs over mud houses get blown away. What is the reason for this?

The correct option is A

Due to low pressure over the roof

When wind with very high speed blows over mud houses with thatched roofs, it creates a low-pressure region over the roof. The wind below the roof is at a higher pressure than the wind above the roof because it has less speed. Thus, a pressure difference is created. Hence, the roof gets blown away.
Moisture on the roof and heaviness of the roof has nothing to do with it being blown away.