What is the advantage of using multiple cylinders in an engine?

Temperature stresses are reduced as the multi-cylinder engine has more cooling surface area due to smaller cylinder bore. The intensity of vibration is sufficiently reduced as the primary and secondary forces are balanced. More power strokes per revolution giving smooth torque output.

Explanation:

a, c, d, e are all applying about success strategies.

real, smaller and upside-down.   so the answer should be b.