One of the legal methods of birth control is

Options

A. by having coitus at the time of day break
B. by a premature ejaculation during coitus
C. abortion by taking an appropriate medicine
D. by abstaining from coitus from day 10 to 17 of the menstrual cycle

Explanation

### Step-by-Step Solution

1. **Understanding Birth Control Methods**: Birth control methods can be categorized into two main types: natural methods and medical methods. It's important to identify which methods fall under each category.

2. **Evaluating the Options**:
- **Option 1**: Coitus at daybreak - This is a natural method but not a widely recognized or effective birth control method.
- **Option 2**: Premature ejaculation during coitus - This is known as the withdrawal method, which is a natural method of contraception.
- **Option 3**: Abortion by taking appropriate medicine - This is known as medical termination of pregnancy (MTP) and is a legal method of birth control when done under medical supervision.
- **Option 4**: Abstaining from coitus from day 10 to 17 of the menstrual cycle - This is known as periodic abstinence, which is also a natural method.

3. **Identifying the Legal Method**: Among the options, the only method that is explicitly recognized as a legal method of birth control is the third option, which involves medical termination of pregnancy (abortion) under the supervision of a registered medical practitioner.

4. **Conclusion**: Therefore, the correct answer to the question "One of the legal methods of birth control is" is **abortion by taking an appropriate medicine**.