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Q.
_____ and____ are unicellular algae, rich in proteins, that are used as food supplements even by space travellers,
Plant Kingdom
Solution:
Chlorella (Green alga), as food supplement is rich in protein and carbohydrates. It yields about $30\%$ proteins, $15\%$ lipids, $30\%$ carbohydrates and $5\%$ ash. Spirulina (blue-green alga) is one of the richest sources of protein and vitamin $B_2$. In long range space exploration, scientist have turned to Chlorella and Spirulina to use them as portable oxygen generators and food sources.