【简答题】图示平面机构在图示位置O 1 A的角速度为w,若要求滑块D的速度,需确定各构件的瞬心位置,以下所确定的瞬心,哪些是正确的?( ) (3.7分)A. E点为三角板ABC的瞬心; B. F点为三角板ABC的瞬心; C. H点为连杆CD的瞬心; D. 为连杆CD的瞬心; E. H点为ABCD的瞬心。
【单选题】听力原文:(A) The classroom is nearly empty. (B) The man is handing out some papers. (C) The board has been written on. (D) The man is facing a group of people.