A:30°S,30°W
B:30°S,60°E
C:30°N,30°W
D:30°S,30°E
(2012·宁波)血液循环系统是人体内的主要运输系统,在体内起着极为重要的作用。下列与血液循环系统有关的说法中,正确的是 ( )
A survey of the opinions of the students _______ that two hours of physical exercise a day _______ acceptable in our campus.