Which of the following is true about top predators? Select one: a. They include bacteria and fungi. b. Their removal increases biodiversity. c. They are likely to be herbivores. d. They are often keystone species. e. They are likely to be producers.

d. They are often keystone species

Explanation:

Top predators in an environment are the largest predators and sits on the top (apex) of the food chain in an ecosystem which do not have any natural predators.

As the top predators relative to its abundance has disproportionately large effect on its natural environment, they are the keystone species most of the time.

Hence option d. They are often keystone species is the right  option.