Assertion (A): Microstrip is very commonly used in microwave integrated circuits (MICs) and RF printed-circuit designs. Reason (R): Microstrip provides easy top-surface access, allowing active and passive discrete components to be conveniently mounted and interconnected. Choose the correct evaluation of A and R.

Introduction / Context:
Microstrip is a planar transmission-line technology fabricated on dielectric substrates with a top signal trace and a bottom ground plane. It dominates MIC and RF PCB layouts for filters, couplers, dividers, matching networks, and component interconnects. This item asks whether the stated reason explains its widespread use.

Given Data / Assumptions:

• Planar process on common substrates (FR-4, alumina, Rogers-type laminates).
• Components (chips, packaged devices) can be soldered or bonded to the top metal.
• Ground reference is the continuous bottom plane.

Concept / Approach:
Microstrip’s popularity arises from ease of fabrication, compatibility with PCB processes, straightforward component access on the top surface, and broad design tool support. The open top makes component mounting and tuning practical. While microstrip has dispersion and radiation compared to stripline, its assembly and prototyping advantages keep it prevalent in MICs.

Step-by-Step Solution:

Verification / Alternative check:
Standard MIC textbooks and application notes show abundant microstrip implementations with top-side component placement and tuning stubs.

Why Other Options Are Wrong:

• B: R is indeed causally related.
• C/D: Deny true statements.

Common Pitfalls:
Assuming stripline is always superior; neglecting assembly and prototyping convenience in practical RF design choices.

Final Answer:
Both A and R are correct and R is correct explanation of A