Consider a Firm Providing Consulting Engineering Services

Consider a firm providing consulting engineering services.In determining this firm's value added to national income,we would start with its total revenue and subtract the cost of (among other things)
1) hard hats for engineers;
2) executive compensation;
3) wages and benefits to in-house engineers.

A) 1 and 2
B) 2 and 3
C) 1 and 3
D) 1 only
E) 2 only