a. The features of an ideal contraceptive are:
1. It should be easily usable by both males and females.
2. It should be easily removable.
3. It should not have any side effects.
4. It should be inexpensive and cost-effective.
5. It should be effective for preventing sexually transmitted diseases or STDs.
b. The natural methods of contraception are:
1. Temperature method: There is a rise in temperature at ovulation due to progesterone and sexual intercourse is avoided at these times.
2. Coitus interruptus: In this method, the penis is withdrawn from the vagina before ejaculation.
3. Lactational amenorrhea: When the female is lactating, ovulation does not occur and at these times, sexual intercourse is safe.