Unicellular would be known to be Chlamydomonas
Volvox would be in a "colonial" organization.
Ulva would be multicellular.
Just by understanding this, we would have to point out from your option which one would be relative to our understanding above, and therefore, your answer would then be the following.
Your correct answer would be the last option, as it would read:
unicellular: Chlamydomonas ---- colonial: Volvox ---- multicellular: Ulva.
Your answer: Last option.
