In $Ulothrix$,sexual reproduction is by

$(i)$ Green algae occur in fresh water,brackish water,and salt water.
$(ii)$ Habitat of Brown algae: fresh water (rare),brackish water,and salt water.
$(iii)$ Some red algae are found in fresh water,mostly occur in salt water,and some are in brackish water.
$(iv)$ Most of the red algae are multicellular.
$(v)$ Red algae may occur in both well-lighted regions close to the water surface and also at great depths in oceans where light penetration is little.
$(vi)$ The cell wall of red algae consists of cellulose $+$ agar.
$(vii)$ $2-8$,equal and apical flagella in green algae.

In the plant kingdom,which of the following plants does not form an embryo?

Which type of algae is found at the greatest depth in the ocean?

Oogamous fertilization involves .......

$Spirogyra$ is a