For reproduction on land, there must be internal fertilization in the reproductive tract such that zygotes can be formed up to a certain cellular level. Thus option A is correct.
What is fertilization?
Fertilization simply can be defined as the process of the mating of male and female gametes. There is internal fertilization in which mating of gametes occurs inside the female reproductive tract and external fertilization in which mating of gametes take place outside the body.
External fertilization is only possible in water as gamets require medium for mating but for reprduction on land internal fertilization is compulsory, so the presence of external fertilization is not an adaptation for reproduction on land. So option A is correct.
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