How can dinoflagellates be harmful to humans?a. They are transmitted by mosquitoes and cause malaria.b. They produce toxins that can be absorbed by clams and other shellfish which, when eaten by people, can lead to paralytic shellfish poisoning.c. They cause amoebic dysentery which leads to severe diarrhea and dehydration.d. They are transmitted by tsetse flies and cause 'sleeping sickness.'