【单选题】From this article, we may infer that the main reason for Ogilvy & Mather growing into the largest and most respected advertising companies is that _____________________.
A.
they had a very capable and thoughtful leader
B.
office heads were mostly open-minded, and always tried to hire people smarter than they were
C.
the company made it a rule to appoint people on their merits
D.
the management of the firm spared no efforts in recruting creative and smart employees