In many places in China,       bicycle is still       poplar means of transportation.

A．a; the

B．/; a

C．the; a

D．the; the

幼儿园氟防龋措施不适宜用（）。

A．氟片

B．涂氟

C．氟水漱口

D．含氟凝胶

E．氟滴剂