There ______________ a pen and two books on the desk. [ ]
A. is
B. are
C. was
D. were
答案:A
慢性风湿性瓣膜病常见的瓣膜损害是()
A.二尖瓣
B.主动脉瓣
C.二尖瓣和主动脉瓣
D.三尖瓣
E.肺动脉瓣