语法与情景会话
Last night , I found ____ UFO in the middle of the square and ____ alien was sitting in it.
A. a ,a 
B. a , an C. an , an D. an ,a
语法与情景会话
Last night , I found ____ UFO in the middle of the square and ____ alien was sitting in it.
A. a ,a B. a , an C. an , an D. an ,a
B