Which group of protozoans consists entirely of parasites?

Which of the following dinoflagellates is known as 'night light'?

Select the $wrong$ statement:

The posterior end of $Amoeba$ is characterized by:

Give scientific reasons: Diatoms are called the pearls of the ocean.

An $X$ reproduces in such great numbers that the water may appear red,producing red tides and killing large marine animals like $Z$. $X$ belongs to $Y$. Identify $X$,$Y$,and $Z$.