**Core Concept**
The Employees State Insurance (ESI) is a social security and health insurance scheme for Indian workers. The ESI scheme is a contributory scheme, where both the employer and the employee contribute to the fund.

**Why the Correct Answer is Right**
The employer's contribution to the ESI scheme is 4.75% of the employee's wages, as per the ESI Act, 1948. This contribution is mandatory for all establishments with 10 or more employees. The employer's contribution is used to fund the medical benefits, cash benefits, and other services provided to the employees under the ESI scheme.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the correct percentage of employer's contribution is not mentioned.

**Option B:** This option is incorrect because the employer's contribution is not 3.75% of the employee's wages.

**Option C:** This option is incorrect because the employer's contribution is not 5.75% of the employee's wages.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that the ESI scheme is a contributory scheme, and both the employer and the employee contribute to the fund. The employer's contribution is used to fund the medical benefits, cash benefits, and other services provided to the employees under the ESI scheme.

**Correct Answer: D. 4.75%**