Although nicotine is probably the well-known chemical in cigarettes, it is not necessarily the one that changes the psyche of the smoker when cigarettes are smoked.

A．All of the top CEOs in America graduate from colleges that are not very elite.
B．It is completely unnecessary to attend elite colleges if one wants to succeed.
C．Elite colleges usually cannot provide excellent graduates for the society.
D．Still a part of top American CEOs are top elite colleges' graduates.