Why animals like frog and fish produce hundreds of eggs while hens and humans produce one egg at a time?

The correct option is D Eggs of frogs and fish are preyed by predators and are exposed to environment.
Eggs of frogs and fish are preyed by predators and are exposed to environment. External fertilization takes place in frogs and fish and thus the challenges are more. Whereas in the case of humans, internal fertilization takes place and thus only one egg is produced, where there are no predator attacks.

So, the correct answer is 'Eggs of frogs and fish are preyed by predators and are exposed to environment.'