He refused to tell us whether he(undertake) the job.

How longthey(dig) the ditch?

he teacher told them since light(travel) faster than sound,lightning(appear) to go before thunder.

The director recommended that she(study) more English before going abroad.

“Have you moved into the new flat? ” “Not yet. The rooms(paint). ”

He fell asleep immediately last night; he must(be) very tired.

He asked me whether my brother(fly) to Beijing.

A great number of small power stations(set up) in their county since liberation.

Those who’d like to visit the exhibition(sign) your names here.

如图(a)，一弹簧上端固定在支架顶端，下端悬挂一托盘：一标尺由游标和主尺构成，主尺竖直固定在弹簧左边;托盘上方固定有一能与游标刻度线准确对齐的装置，简化为图中的指针。现要测量图(a)中弹簧的劲度系数，当托盘内没有砝码时，移动游标，使其零刻度线对准指针，此时标尺读数为1.950cm;当托盘内放有质量为0.100kg的砝码时，移动游标，再次使其零刻度线对准指针，标尺示数如图(b)所示，其读数为cm。当地的重力加速度大小为9.80m/s2，此弹簧的劲度系数为N/m(保留3位有效数字)。