Jon P. answered • 07/18/15

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The period of a pendulum with a small angle of oscillation is approximately 2π√(L/g). However, there are actually additional terms in the equation for the period that increase as the angle of oscillation increases. So the larger the angle, the larger the additional terms are, and therefore the longer it takes for the pendulum to make one oscillation.

As each tick of the clock (one oscillation) takes longer, the clock appears to runs slower. So the answer is a.