纪念章有哪些种类？
参考答案：①国防服役纪念章；
②卫国戍边纪念章；
③献身国防纪念章；
④和平使命纪念章；
⑤执行作战和重大任务纪念章。
-Is your sister at home, Dennis?
-No, she isn't. I think she _ _ the piano in Anna's living room. [ ]
A. can play
B. could be playing
C. had played
D. plays
液化气体的用途有哪些?
