Unicellular protists with two flagella that are photosynthetic and cause red tides are called
a amoebas
b ciliates
c dinoflagellates
d euglenoids

C dinoflagellates

A flagella (or flagellum plural) is a long strand like structure that is located in the front end part (more like a tail in front). It flips to the left and right in order for the organism to move. It is connected to the reservoir, which contains the storage of food for the organism.

These unicellular organisms are responsible for breaking down materials in the earth. They assist with the decomposition of the dead and decaying matter that can be found on the earth's surface. This break down also makes up natural fertiliser for the plants which then grow up fertilised. These unicellular organisms are also an essential part of the nitrogen cycle. They change the nitrogen from the environment and turn them into absorbable nitrates for the plants, which is an essential part of the plants' food.

It should be cryosphere and hydrosphere