Zhangzhou property escrow elevator

According to the kinetic energy theorem, a and b are obtained:

For the object: WN-mgH= 12mv2, and the work done by the floor supporting the object is WN = MGH+ 12mv2. So, AB is wrong.

C according to the kinetic energy theorem: WF-(M+m)gH= 12(M+m)v2, the work done by the cable tension is WF = (m+m) GH+ 12 (m+m) V2. So, C is wrong.

D, according to the kinetic energy theorem:

For elevator: W = 12Mv2, that is, the work done by the resultant force on elevator m is 12Mv2. Therefore, d is correct.

So choose d