题目

You look worried . Is _______ all right ? A. something    B. anything        C. everything        D. nothing        答案：C18．心脏内有瓣膜，保证血液在心脏内的流向是（　　）A．心房→心室→动脉B．心室→心房→静脉C．心房→心室→静脉D．心室→心房→动脉