What is common among $Trypanosoma$,$Noctiluca$,$Monocystis$,and $Giardia$?

Euglena is a:

African sleeping sickness or Gambiense fever is caused by

Which organism is considered a connecting link between plants and animals?

The given statements are some characters of a particular group of Kingdom $Protista$.
$(i)$ Most of them are freshwater organisms found in standing water.
$(ii)$ They have a protein-rich layer (called pellicle) which makes their body flexible.
$(iii)$ They have two flagella,a short and a long one.
$(iv)$ Though they are photosynthetic in the presence of sunlight,but in the absence of sunlight they behave like heterotrophs by predating on other smaller organisms.
Identify the correct group on the basis of these characters.

The dinoflagellate,which is also known as the sea sparkle,is ..........