More than _______ of the classmates in my class ____ fond of pop music．[ ]

A．two-third, is  

B．two-thirds, is  

C．second-third, are  

D．two-thirds, are

汽车在平直的公路上以10 m/s的初速度运动，经30 s到Ａ点速度达到20 m/s后开始刹车，又经5 s停下，则汽车在Ａ点以前30s的加速度等于　　m/，到Ａ点后的加速度等于___________m/。