Three-input OR expression: Choose the correct Boolean expression for a 3-input OR gate with inputs A, B, C and output X.

Introduction / Context:
Boolean notation links directly to gate symbols and truth tables. The OR operator is denoted by a plus sign and produces a HIGH output if any input is HIGH.

Given Data / Assumptions:

• Inputs: A, B, C.
• Standard operators: “+” for OR, “·” for AND.

Concept / Approach:
A 3-input OR gate is written as the sum of the three input literals: X = A + B + C.

Step-by-Step Solution:
Identify the intended function → OR across three signals.Write directly → X = A + B + C.

Verification / Alternative check:
Construct a truth table and verify that whenever any input is 1, X is 1; only A = B = C = 0 yields 0.

Why Other Options Are Wrong:
X = A + B: ignores C.X = ABC: AND of three inputs.X = A + BC or (A + B)C: mixed expressions not equivalent to a plain 3-input OR.

Common Pitfalls:
Confusing OR with mixed sum-of-products structures.

Final Answer:
X = A + B + C