Pendulum takes 1 second to move from x to y so it's frequency equal

if it takes 1 second to move from x to y. You haven't specified if x and y are extreme point or x is extreme and y is equilibrium point

I.If both are extreme points the period is T=1*2=2s

f(frequency)=2π/T(period)

f=6.28/2=3.14Hz

II.If x is an extreme point and y is equilibrium

T=4*1=4s

f=6.28/4=1.57Hz

the answer would be c