Question

Crabs undergo
fertilisation whereas humans undergo
fertilisation.

• A. double
• B. internal
• C. single
• D. external

Answer 1

Answer: (B), (D)

The correct options are
B internal
D external

Fusion of male and female gametes to form a diploid zygote is called fertilisation. When fertilisation occurs outside the body it is called external fertilisation. Mainly aquatic animals such as crustaceans, molluscs and most fishes exhibit external fertilisation.
In internal fertilisation, fusion occurs within the organism, like in humans and most mammals.