细菌污染输血反应的发生率为多少？（）
A、1％～2％
B、l％～3％
C、2％～4％
D、3％～5％
E、2％～6％
参考答案：B
一个直角三角形中的一个锐角是另一个锐角的2倍，则这个三角形中最小锐角是[ ]
A．450。
B．30。
C．25。
—Mr Wang was caught in a snowstorm yesterday.
—I have known that，and_______his new car was completely destroyed.
A．hopefully
B．fortunately
C．thankfully
D．unfortunately
