Ans:A
As in case of internal fertilisation risk of disease transmission is higher than external fertilisation.

Advantages of Internal Fertilization over External Fertilization

Internal fertilization is a reproductive strategy where the sperm is deposited inside the female reproductive tract, and fertilization takes place internally. In contrast, external fertilization occurs outside the body where the eggs and sperm are released into the environment. While external fertilization is common in aquatic organisms, internal fertilization is more prevalent in terrestrial animals. The following are some advantages of internal fertilization over external fertilization:

Decreased Risk of Disease Transmission
Internal fertilization reduces the risk of disease transmission compared to external fertilization. This is because the sperm and egg are protected from external pathogens and predators, which can lead to infections or predation. The female reproductive tract has several mechanisms that prevent pathogen entry, such as mucus secretion and immune system responses.

Minimal Waste of Gametes
Internal fertilization minimizes the waste of gametes. Unlike external fertilization, where millions of gametes are released into the environment, internal fertilization ensures that the sperm and egg meet in a controlled environment, increasing the chances of fertilization. This reduces the energy spent on producing gametes and increases the reproductive success of the individual.

Greater Chance of Individual Egg Fertilization
Internal fertilization enhances the chances of individual egg fertilization. This is because the sperm is deposited directly at the site of fertilization, increasing the chances of successful fertilization. In external fertilization, the sperm and egg are released into the environment, and the chances of successful fertilization are reduced due to competition between sperm and predation.

Relatively Longer Time of Egg Protection
Internal fertilization provides relatively longer protection for the developing egg. The egg is protected from external predators and environmental factors, ensuring its survival until hatching. In external fertilization, the egg is exposed to several risks, such as predation, infections, and environmental fluctuations, reducing its chances of survival.

Conclusion
Internal fertilization is a reproductive strategy that offers several advantages over external fertilization. It reduces the risk of disease transmission, minimizes the waste of gametes, enhances the chances of individual egg fertilization, and provides relatively longer protection for the developing egg. These advantages have led to the evolution of internal fertilization in several terrestrial animals, ensuring the survival of their offspring in a competitive environment.