_____ is the population of China? It is about 1,300,000,000.

A．How many

B．How much

C．What

D．How

凌汛是指某个河段因冰凌堵塞，水流不畅，引起水位猛涨的现象。黄河的部分河段每年冬季和春季都会发生凌汛，请判断图中黄河干流上易发生凌汛的河段是(　　)

A．ab段

B．bc段

C．cd段

D．de段