过期产儿是指
A.胎龄>28周至40周B.胎龄>28周至<42周C.胎龄≥37周至<42周D.胎龄≥40周至<42周E.胎龄<37周的婴儿
参考答案:D
Did you have fun___in the river? [ ]
A. swim
B. swimming
C. to swim
D. swam
我国标准规定:工频安全电压的上限值为()。