Step 1: Understanding the Concept:
Household linens are manufactured according to standardized dimensions to fit various mattress sizes, such as Single, Double, Queen, and King.
Step 2: Detailed Explanation:
Standard mattress sizes dictate the minimum dimensions required for flat sheets to allow for proper tucking under the sides:
- A standard King-size mattress measures approximately $76 \times 80$ inches (or $72 \times 78$ inches in Indian standards).
- To cover this surface area and provide a sufficient drop on all three sides for tucking, a flat King-size bed sheet must have generous dimensions.
- The standard commercial size for a flat King-size bed sheet is approximately 108 x 110 inches (or $274 \times 279\text{ cm}$).
Let us review the other options:
- 90 x 110 inches: More typical of a Queen-size flat sheet.
- 90 x 104 inches: Standard double bedsheet dimensions.
- 112 x 118 inches: Exceeds standard king dimensions and is uncommon except for custom over-sized mattresses.
Therefore, $108 \times 110$ inches is the correct measurement.
Step 3: Final Answer:
A flat king-size bed sheet typically measures 108 x 110 inches.