In the following sentence, four words or phrases have been underlined. One of…

Concept

In the structure “one of the + plural noun + relative clause,” the relative pronoun (who/that/which) refers back to the PLURAL noun, not to the singular “one.” Therefore the verb inside the relative clause must be PLURAL and agree with that plural noun. The phrase “one of the” does not make the following verb singular.

Application

1. Identify the noun the relative clause describes: “one of the five books that ... launched.” The clause beginning with “that” describes “books,” which is plural.

2. Make the relative-clause verb agree with “books” (plural): the correct verb is “were launched,” not “was launched.”

3. So the underlined “that was” carries the error; it should read “that were” to match the plural “books.”

Cross-check the other underlined parts

• “This” – a singular demonstrative correctly pointing to the single book the speaker is highlighting; grammatically fine.

• “one of the” – the standard partitive phrase introducing a member of a larger group; used correctly here.

• “at” – the right preposition for naming the venue/place of an event; used correctly.

Reading the corrected sentence confirms the fix: “This is one of the five books that were launched yesterday at Vigyan Bhawan.” The only grammatically incorrect underlined part is “that was.”