Answer:
D: 18
Explanation:
Airplanes = 36%
Automobiles = 53%
Trains = 2%
----------------------------
91% Chose these types of transportation
The rest chose boats
100% - 91% = 9%
So 9% chose boats
People who chose boats = people surveyed * percent who chose boats
200 people were surveyed and 9% = .09 chose boats
People who chose boats = 200 * .09
= 18