How do whales, bats, and dolphins use echolocation.
a. to scare away predators
b. to orient themselves and to find food
c. to attract mates
d. to tell other animals of their species where they are

B. To orient themselves and to find food

Since they cannot see very well or even at all in some cases, these animals use echolocation instead to orient themselves, to find where they are, and to find food.

when it is at an intermediate population density

sex cells are usually half's then they find another half and make a fertilize egg