Choose the correct plural form of the word given below:Alga

The correct answer is Option (4) → Algae

Plural of nouns ending in -a (from Latin):

Some nouns that came into English from Latin end in -a. They change -a to -ae in the plural. So alga → algae. An alga is a very simple plant with no roots or leaves. It grows in water or on wet surfaces. “Algi” is wrong because the -i ending belongs to nouns that end in -us.