Which of the Following Is True of Advertising Agencies

Which of the following is true of advertising agencies?

A) Advertising agencies can be helpful,but they are always more expensive than a firm doing its own advertising work.
B) Advertising agencies must be selected very carefully,since most require long-term contracts.
C) Advertising agencies that are smaller in size will probably continue to play an important role,despite the creation of mega-agencies.
D) Advertising agencies usually specialize in one particular type of work,such as sales promotion planning or website design.
E) None of these answers is correct.