IgM占血清总Ig的（）。
A.10％～15％
B.1％～5％
C.15％～20％
D.20％～25％
E.5％～10％
参考答案：E
----Have they finished the project?
---- Yes. By the end of last month, they ______ it. Now they ______ on a new one.
A．had finished; are working
B．had finished; work
C．have finished; are working
D．have finished; work
凡士林灭菌方法，应采用
A．热压灭菌
B．干热空气灭菌
C．紫外线灭菌
D．流通蒸汽灭菌
E．煮沸灭菌法
