17. We are ______ discount flights to San Francisco.
(A) checking out
(B) checking on
(C) checking into
(D) checking off
答案:登入後查看
統計: A(39), B(41), C(77), D(8), E(0) #217427
統計: A(39), B(41), C(77), D(8), E(0) #217427