已知对任意实数x，有f(-x)=-f(x)，g(-x)=g(x)，且x＞0时f′(x)＞0，g′(x)＞0，
则x＜0时                                                              (    )

A：f′(x)＞0，g′(x)＞0

B：f′(x)＞0，g′(x)＜0

C：f′(x)＜0，g′(x)＞0

D：f′(x)＜0，g′(x)＜0