Following are the singular and plural nouns in the sentence.
astronauts -P
crowd - S
What are the examples of singular and plural nouns?
The majority of singular nouns can be made plural by adding a -s to the end. Depending on what letter a noun finishes in, pluralization rules can vary greatly. Irregular nouns must be learned or looked up in a dictionary because they do not adhere to the plural noun rules.
1. Add 's' to the end of normal nouns to make them plural.
cat – cats
2. Add the letter "es" to the end of the singular noun if it ends in s, ss, sh, ch, x, or z to make it plural.
Trunk - Trunks
bus - buses
To learn more about singular and plural nouns from given link
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