The underlined part of the first sentence "Doctors are of the opinion that'"" means ______.

A．Within a few generations, most people may live much longer than they do now.
B．More than 12,000 Americans are over 100 years old.
C．Doctors and scientists disagree over the question of man's possible life span.
D．Man's normal period of growth is approximately as long as that of animals.

A．the leisurely 21-day coach tour of Italy
B．the working holidays for 1 -3 months on a farm
C．the splendid 14-day trip around the island
D．the interesting 2-week stay in a luxurious hotel