Answer
(a) decrease
(b) I
Work Step by Step
(a) We know that for a constant force, the acceleration and mass are inversely proportional. Hence, when both masses are increased by 1 kg then the acceleration decreases.
(b) We know that the correct option is statement (I) -- that is, the net force acting on the blocks is the same, but the total mass that must be accelerated is greater.
