Find the area of the composite shape

Answer is in the file below

cutt.ly/rzNrBcz

12 ft * 10 ft = 120 sq ft

½ * 6 ft * 7 ft = 21 sq ft

120 sq ft - 21 sq ft = 99 sq ft (it is area of the composite shape)

I think it's Letter B, survey since they are asking about people's opinion (their favorite color), and it is more on a descriptive research. It doesn't really matter that it's the fifth person to board the train or not. 
It is not Letter A since a controlled experiment is an experimental research by nature and would specifically deal with scientific procedures.
I'm not so with the Observational Survey. Both are ways of gathering information, but a survey is completed by another person (meaning the person they asked) while the observational survey is done by the observer only.