两个自然数的积一定是合数。( )
参考答案:错
解析:[解析] 1和3为两个自然数,积为3,是质数。
—Come on,Kitty.
—Oh, good heavens! Both my legs are nearly to give out. I_______ for hours like a dog.
A.have been walking
B.had walked
C.was walking
D.walked
()是保险金给付的来源。
A.毛保费
B.附加保费
C.纯保费
D.管理费用