The correct option is A Zero
Friction force is trying to uppose the motion so,
fs=μmgcos300=0.7×10×10×√32
fs=35√3=60.62 N
Gravitational force helping in motion i.e,
F=mgsin300=10×10×12=50 N
Since fs>F, this means friction force is sufficient to oppose gravitational force. So, tension will be Zero