A block of mass m on a frictionless horizontal surface is connected by a light, inextensible string that passes over a frictionless pulley to a hanging mass M. A student chooses a system consisting of both blocks and the string, but not the pulley or Earth. Which of the following forces acting in the original situation will cancel when the net force on the chosen system is calculated?
a) The gravitational force on the hanging mass M.
b) The normal force exerted by the table on the block of mass m.
c) The tension exerted by the string on each block.
d) The gravitational force on the block of mass m.