形状不规则的均匀薄板可用悬挂法找重心,图中虚线是第一次悬挂时拉力的作用线,试在图中确定该薄板的重心。(用O表示,保留作图痕迹)
(1) How many units must we learn this term? (改为被动语态)How many units____ this term?(2)It took him two hours to finish reading the novel.(改为同义句)He ____ two hours____ the novel.(3)Parents should allow their children to choose their own clothes.(改为被动语态)Children ____ to choose their own clothes.(4)I was asked to clean up the room by my teacher.(改为主动语态)My teacher____ to clean up the room.(5)I believe that Lucy is allowed to perform a play for the old people.(改为否定句)I____ believe that Lucy____ to perform a play for the old people.