静脉系统来源的血栓栓子可引起（）。
A.心肌梗死
B.脑梗死
C.肝梗死
D.肺动脉主干栓塞
E.肺出血性梗死
参考答案：D, E
It is _____ to come into the teacher's office without his permission. [ ]
A. bad manner
B. a manner
C. manners
D. bad manners
I am thirsty. I want to drink some ______. [ ]
A. apples
B. oranges
C. ice cream
D. orange
