According to the stress analysis of block A and the equilibrium condition, the rope tension FT=mAg is constant.

The force analysis of block B is influenced by gravity G, rope tension mAg, ground support force FN and friction force F, as shown in the figure:

Horizontal direction: Ff=mAgcosθ.

Vertical direction: FN=G-mAgsinθ.

The object speed b slowly moves to the left for a short distance, θ becomes smaller, mAgcosθ becomes larger, mAgsinθ becomes smaller, and Ff becomes larger.

FN also becomes larger. Option c is correct.

So choose: C.