Some fish and amphibians have which detect electrical fields that them navigate through dark, murky waters.

a. photoreceptors
b. olfactory receptors
c. electroreceptors
d. thermoreceptors

Electroreceptors. Fishes use this ability since the water is a better electrical conductor than air. It helps them to know their location, to recognize their location in the water. They can also find objects due to the electrical fields. This is the correct.

The answer is C. Electroreceptors are used by certain species of fish to detect electrical fields. This can be helpful in finding prey or avoiding predators. It is a specialized ability, though, and many animals do not posses this trait.

They get pregnant at younger ages

Giga is the second highest prefix on the normal scale, the first is terra.