再生障碍性贫血的发病机制是（）
A.造血原料缺乏
B.无效红细胞形成
C.红细胞破坏过多
D.骨髓造血功能低下
E.脾功能亢进
参考答案：D
As Britain’s first and only female Prime Minister, Thatcher was famous for her_____ style, and thus she was called the“Iron Lady”．
A．constant
B．tough
C．rough
D．mild
－ _____ he ever _____ abroad?
－ No, never. [ ]
A. Did, go
B. Is, been
C. Has, been
D. Has, gone
