Which type of sexual reproduction occurs in algae?

What does the cell wall of algae consist of?

Which of the following organisms cannot fix nitrogen?
$A.$ Azotobacter
$B.$ Oscillatoria
$C.$ Anabaena
$D.$ Volvox
$E.$ Nostoc
Choose the correct answer from the options given below:

Ulothrix is

Which of the following statements are true regarding the figure given below?
$(i)$ It shows oogamy and post-fertilization development.
$(ii)$ Male gamete is small and motile.
$(iii)$ Stored food is floridean starch.
$(iv)$ Pectin,cellulose,and polysulphate esters are present in the cell wall.

Most primitive members of the plant kingdom are