Logic Gates question from NEET 2021

Answer: (c)

1. $y = A \cdot B + \overline{B \cdot C}$ (AND, NAND, then OR).
2. Before $t_2$: $B = 0$, so $\overline{B \cdot C} = 1$ and $y = 1$.
3. $t_2$ to $t_3$: $C = 0$, so the NAND gives 1; $t_3$ to $t_4$: $A = B = 1$, so $A \cdot B = 1$.
4. After $t_4$: $B = 0$ again, so $y = 1$. Thus y stays at 5 V all the time.
5. So the answer is (c).