That little boy doesn't feel like _____ out today, _______ her sister would like to go shopping.

A．going, and

B．to go, and

C．going, but

D．to go, but

疲劳损伤积累理论认为，当零件的应力低于( )时，应力循环不会对零件造成损伤。

A．强度极限

B．屈服极限

C．弹性极限

D．疲劳极限