74LS138 decoder — Evaluate: “Output 6 is selected when A0 = 1, A1 = 1, A2 = 0 (with the device enabled).”

Introduction / Context:
The 74LS138 is a 3-to-8 decoder with active-LOW outputs Y0–Y7. It asserts exactly one output LOW based on the binary code on inputs A (LSB), B, and C (MSB) when properly enabled. The prompt tests correct output indexing for a specific input pattern.

Given Data / Assumptions:

• Inputs: A0 ≡ A (LSB), A1 ≡ B, A2 ≡ C (MSB).
• Enable conditions satisfied: G1 = 1, G2A = 0, G2B = 0.
• Outputs are active LOW; “selected” means driven LOW.

Concept / Approach:
The output index equals the binary value ABC (with C as MSB, A as LSB). For A2 A1 A0 = 0 1 1, the binary value is 3, so Y3 goes LOW, not Y6. Therefore, saying “Output 6 is selected” for 0 1 1 is incorrect.

Step-by-Step Solution:

Verification / Alternative check:

Why Other Options Are Wrong:

Common Pitfalls:

Final Answer: