题目

His parents insisted that he __________English well when he was in junior school. A . would learn B . must learn C . learned D . learn 答案：D用一根长1 m的轻质细绳将一幅质量为1 kg的画框对称悬挂在墙壁上，如图所示．已知绳能承受的最大张力为10 N，为使绳不断裂，画框上两个挂钉的间距最大为(g 取10 m/s2)(　　) A. m                            B. m C. m                                D. m