题目

设人在20℃的环境中产热速率为a1，散热速率为b1；进入0℃环境20min后的产热速率为a2，散热速率为b2。以下有关产热速率与散热速率大小比较正确的是（   ） A．a1＝b1，a2＝b2                            B．a2＜a1，b1＜b2       C．a1＜b1，a2＞b2                            D．A、B两项都对The policeman came up to the house, whose door was open, _____ there for a while, and went in.A.to standB.standingC.stoodD.stand