(N/A) Algae reproduce asexually by a variety of spores under different environmental conditions.
These spores and the conditions under which they are produced are as follows:
$(a)$ Zoospores: These are flagellated,motile spores. They are produced under favourable conditions.
$(b)$ Aplanospores: These are thin-walled,non-motile spores. They are produced under unfavourable conditions.
$(c)$ Hypnospores: These are thick-walled spores that help the organism survive during highly unfavourable conditions.
$(d)$ Akinetes: These are thick-walled,non-motile resting spores formed from vegetative cells,typically under unfavourable conditions.