A shop sign of weight 30 N hangs motionless from a vertical cord. Which statement about the forces on the sign is correct?
a) They are unbalanced because only the weight of 30N acts downward and no upward force acts.
b) They are balanced even though the net force is 30N upward.
c) They are balanced because the tension in the cord is 30N upward.
d) They are unbalanced because the tension must be greater than the weight to keep the sign from falling.