Four-input OR expression: Select the correct Boolean expression for a 4-input OR gate with inputs A, B, C, and D and output Y.

Introduction / Context:
Recognizing canonical Boolean forms is indispensable for design and verification. The OR function outputs HIGH if any input is HIGH.

Given Data / Assumptions:

• Inputs: A, B, C, D.
• Operator “+” denotes OR; “·” denotes AND.

Concept / Approach:
A 4-input OR gate is written as the sum of all inputs: Y = A + B + C + D.

Step-by-Step Solution:
Map function → OR.Write as sum of literals → A + B + C + D.Thus Y = A + B + C + D.

Verification / Alternative check:
Truth table shows output HIGH for any case with at least one input HIGH, matching the sum form.

Why Other Options Are Wrong:
A·B·C·D: AND of all four inputs, not OR.Minus sign and dollar sign are not standard Boolean OR operators.(A + B)(C + D): equals AC + AD + BC + BD, which is not a simple 4-input OR.

Common Pitfalls:
Mixing arithmetic and Boolean operators or expanding incorrectly.

Final Answer:
Y = A + B + C + D