易发生蒂扭转的卵巢肿瘤是（）。
A.浆液性囊腺瘤
B.成熟畸胎瘤
C.内胚窦瘤
D.黏液性囊腺瘤
E.纤维瘤
参考答案：B
—I bought this shirt for 35 yuan yesterday.
—It’s on sale today for only 29. You should have waited.
—Oh, really? But how ________ I know?
A．would
B．can
C．did
D．do
推广国际贸易“（）”实现全国通关一体化。
