国家英语课程要求从三年级起开设英语课，（）是六年级结束时应达到的基本要求。

单项选择题() Yellow River is the second longest river in our country.

A. /
B. The
C. An
D. A

单项选择题—Would you like to play basketball with us —Yes, I'd love to. ______ I'm afraid I have no time.