问题补充：
—What Yu Ping usually in her free time?
—She usually goes to the library.
A. do; do
B. is; doing
C. does; does
D. does; do
答案：
A. do; do
B. is; doing
C. does; does
(答案→)D. does; do
解析：句意：余萍通常在空余时间做什么？她通常去图书馆。句中有usually ，所以时态是一般现在时，主语Yu Ping 是第三人称单数，助动词应用does,实意动词用原形 do，故选D。
