Flco hotel

Force analysis of sled, as shown in the figure:

A, the supporting force does work W N =Nlcos90 =0 0, so A is wrong;

B, gravity work W G =mglcos90 =0 0, so b is correct;

C, the tensile work is W F =Flcoθ, so C is correct;

D, sled vertical force balance: N+Fsinθ=mg.

Then N=mg-Fsinθ.

f=μN=μ(mg-Fsinθ)

Then friction does work W f =-fl=-μ(mg-Fsinθ)l, so d is wrong;

So: BC.