Explanation

Singular noun: Mouse

Plural noun: Mice 

The plural for a computer mouse is either "mice" or "mouses" according to most dictionaries, with "mice" being more common.

Explanation

The plural form of fish is also fish.

Fish has no plural form.

Similarly, sheep has no plural form.

Explanation

Most nouns form plurals by adding –s.

“Banana” follows the regular plural rule.

Explanation

Criteria is a plural noun. Its singular form is criterion. 

options are incorrect

Index is a singular noun. Its plural forms are indices (often used in formal/academic contexts) or indexes (more common in general usage).

Analysis is a singular noun. Its plural form is analyses.

Crisis is a singular noun. Its plural form is crises. 

Explanation

Bird → Birds shows singular to plural.

The plural of person is people.