Answer:
Internal fertilisation
Step-by-step explanation:
The fact that the sperm and the egg fused to create a zygote while inside the female body, is reason to state that the answer is "internal fertilisation".
Asexual reproduction does not occur in crocodiles, and the other option of external fertilisation would occur in frogs, where the female lays eggs in a pond, and a male frog will fertilise it at a later stage.