For a logic gate abstraction, how many input signals can a gate legally accept in digital design practice?

Introduction / Context:
Logic gates are defined by a Boolean function mapping N inputs to a single output. While textbooks often show 2-input gates for simplicity, practical gates can be unary (one input) or have many inputs (3, 4, 8, or more). Understanding this flexibility avoids artificial constraints during circuit design or exam questions.

Given Data / Assumptions:

• Gate = combinational device with fixed truth table.
• Technology could be TTL, CMOS, ECL, etc.
• No specific fan-in limit is imposed by the question.

Concept / Approach:

Unary gates (NOT/inverter, buffer) accept one input. Multi-input gates (AND, OR, NAND, NOR) accept 2 or more inputs; many families offer 3-input, 4-input, or 8-input variants. Therefore the correct general statement is that a gate may have one input or more than one input. The option claiming “two only” is false; two is common but not exclusive.

Step-by-Step Solution:

Verification / Alternative check:

Standard logic catalogs list NAND/NOR/AND/OR in multiple input counts; data sheets confirm functional equivalence across different fan-in sizes.

Why Other Options Are Wrong:

'two only' is overly restrictive. 'one' or 'more than one' alone are incomplete. 'None of the above' fails because a correct inclusive statement exists.

Common Pitfalls:

Assuming all logic gates are 2-input due to common diagrams, and ignoring fan-in limits that are technology-specific rather than theoretical.

Final Answer:

both (a) and (b)