Step 1: Understanding the Question:
The topic is Computer Hardware Specifications. This question asks for the physical dimension (thickness) of a standard Compact Disc Read-Only Memory (CD-ROM). These specifications are part of the rigid international standards (the Rainbow Books) that ensure any disc produced by any manufacturer can fit into and be read by any drive made by any other manufacturer. Precise knowledge of these measurements is often required in technical engineering and hardware exams.
Step 2: Key Formulas and approach:
The approach involves referencing the "Red Book" standard for Compact Discs. These are fixed physical constants:
1. Diameter = 120 mm.
2. Thickness = 1.2 mm.
3. Center Hole Diameter = 15 mm.
We compare the standard measurement (1.2 mm) against the choices provided in the question to determine if a match exists.
Step 3: Detailed Explanation:
According to the international standard for optical discs, the thickness of a standard CD is exactly 1.2 mm.
This 1.2 mm thickness consists of the polycarbonate plastic substrate, the reflective metallic layer, and the protective lacquer coating.
Let's look at the options: (A) 1.22 mm is close but mathematically distinct from the 1.2 mm standard. (B) 1.5 mm is far too thick. (C) 0.66 mm is approximately half the thickness (closer to a single layer of a DVD).
Because the industry-standard value is 1.2 mm and it is not explicitly listed among the numerical options, the most accurate choice is "None of these".
Step 4: Final Answer:
The standard thickness of a CD ROM is 1.2 mm. Consequently, the correct choice is (D) None of these.