风湿性心脏病病人,出现吞咽困难,最可能是因为
A.左心室明显扩大B.左心房明显扩大C.右心房明显扩大D.右心室明显扩大E.肺动脉明显扩大
参考答案:B
After ten years' absence she came back, only to find her old house was not ________ it used to be.[ ]
A.which
B.what
C.when
D.how
(1)如图(a)所示是在水平公路行驶的汽车,请画出汽车牵引力的示意图;
(2)完成图(b)所示的光路.