Which of the following is the wrong pair of singular and plural nouns?

A part of the sentence used to identify a person, place, animal, or thing is called a noun. A noun can be singular or plural, based on the number of nouns and pronouns used in the sentence. The plural of 'man' is 'men', 'child' is 'children', and 'mango' is 'mangoes'. Thus, except for 'theifs' all the options are correct. To convert 'thief' into plural, 'eves' needs to be added in place of 'f'. 'Thieves' is, thus, the correct plural form.