Explanation:

In digital electronics, a logic gate is a fundamental building block that performs a specific logical operation on one or more binary inputs and produces a single binary output. There are several types of logic gates, including AND, OR, NAND, NOR, XOR, and XNOR gates.

Inverter Gate:
An inverter gate, also known as a NOT gate, is a logic gate that produces an output that is the complement of its input. In other words, if the input is a logic high (1), the output will be a logic low (0), and vice versa. The symbol for an inverter gate is a triangle pointing towards the input with a small circle at its tip.

Logic High:
In digital electronics, a logic high refers to a voltage level that represents a binary value of 1. It is typically represented by a higher voltage compared to the logic low state. The exact voltage level for a logic high depends on the specific digital system and the technology used.

Explanation of the Answer:
According to the given question, the logic gate acts as an inverter when one of its inputs is connected to logic high. This means that when one of the inputs is a logic high (1), the output of the gate will be the complement of the other input.

NAND Gate:
A NAND gate is a logic gate that performs the logical operation of an AND gate followed by a NOT gate. It produces a logic high output only when both of its inputs are logic low (0). Therefore, a NAND gate does not act as an inverter when one of its inputs is connected to logic high.

EXOR Gate:
An EXOR gate, also known as an XOR gate, is a logic gate that produces a logic high output when the number of logic high inputs is odd. It produces a logic low output when the number of logic high inputs is even. Therefore, an EXOR gate does not act as an inverter when one of its inputs is connected to logic high.

EX NOR Gate:
An EX NOR gate, also known as an XNOR gate, is a logic gate that produces a logic high output when the number of logic high inputs is even. It produces a logic low output when the number of logic high inputs is odd. Therefore, an EX NOR gate does not act as an inverter when one of its inputs is connected to logic high.

Conclusion:
The only logic gates that act as an inverter when one of their inputs is connected to logic high are the NAND gate and the EX NOR gate. Therefore, the correct answer is option 'D' - Both a and b.