a
When the pendulum $A$ with time period $\frac{5 T}{4}$ completes phase of $2 \pi$ in $\frac{5 T}{4},$ the other pendulum $B$ leads by phase $\frac{\pi}{2}$.
So after $4$ oscillations of pendulum $A$ i.e. after $5 T$, pendulum $B$ leads by $2 \pi$ i.e they come in phase.
i.e. after $5$ oscillations of small pendulum (Time taken $=5 T$ ), they will again come in the same phase.