下列大环内酯类抗菌药物,对肺炎支原体作用最强的是()
A.红霉素
B.吉他霉素
C.罗红霉素
D.阿奇霉素
E.交沙霉素
参考答案:D
I have been living in the United States for twenty years,but seldom _______ so lonely as now.
A.have I felt
B.I had felt
C.I have felt
D.had I felt
如图所示的事例中,属于运用了重力方向的是 [ ]
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