Valentine's Day is almost here: ________ time of year when some of us enjoy ________ company of a loved one, while others feel lonely being alone.

A．the；不填　

B．a；a

C．a；the

D．the；a

计算机售票系统中Fl键的用途是（）。

A.输入席别

B.输入日期

C.选择用途

D.交易显示