The output of a logic gate is ‘$1$’ when all its inputs are at logic ‘$0$’. Then gate is either
- a $\text{NAND}$ or an $\text{EX-OR}$ gate
- a $\text{NOR}$ or an $\text{EX-NOR}$ gate
- an $\text{OR}$ or an $\text{EX-NOR}$ gate
- an $\text{AND}$ or an $\text{EX-OR}$ gate