Multiple-choice method: let m2=0, then vmax=0, only A meets, so choose A..

Calculation method:

Opening balance: k * x1= (m1+m2) g.

At the maximum speed, the spring force is equal to m 1 gravity: k * x2 = m1* g.

Mechanical energy balance: 1/2k*x 1? - 1/2k*x2？ = 1/2m 1*v？ +m 1*g*(x 1-x2)

The answer is the same as a.