Answer 1

Forces acting on the pulley A : 

1. A tension exerts electromagnetic force between the string and pulley A.
2. A pair of gravitational force between the Earth and pulley.

Forces acting on the boy :

1. A tension exerts electromagnetic force between the string and the boy.
2. A pair of gravitational force between the Earth and the boy.

Forces acting on the block C :

1. A tension exerts electromagnetic force between the string and block C.
2. A pair gravitational force between block C and the Earth.