The antibiotic "chlorellin" is extracted from which genus?

Which of the following statements are applicable to brown algae?
$(I)$ They contain pigments like chlorophyll $a$,chlorophyll $c$,carotenoids,and xanthophylls.
$(II)$ They vary in color from olive green to various shades of brown.
$(III)$ Food is stored as complex carbohydrates,in the form of laminarin or mannitol.
$(IV)$ The cell wall is composed of cellulose and algin.
$(V)$ The cell wall is covered on the outside by a gelatinous coating of algin.

Which of the following is an incorrect characteristic of brown algae?

Give common characteristics of green algae or Chlorophyceae.

$Acetabularia$ is a:

Which structure of $Spirogyra$ is flagellated?