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Wren & martin says :
When the subject of a verb is a relative pronoun care should be taken to see that the verb agrees uin number and person with the antecedent of the relative : as,

1. This is one of the most interesting novels that have (not has) appeared this year
(The antecedent of that is novels, not one)

2. This is the only one of his poems that is (not are ) worth reading.
( here the antecedent of that is one)

Now, Can you this exercise.

1. She is one of the best mothers that (has or have) ever lived.
2. This is one of the songs that (was or were) most popular.
3. Tyranny is one of those evils which (tends or tend) to perpetuate (itself or themselves).
4. Ambition is one of those that( was or were) most popular.

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Hello Aastha

I would say that the plural form is correct in all these cases. The antecedents here are mothers, songs, evils, and 'those'.

To test this answer:

'This is one of the songs that were most popular in the war'. =
'Of the songs that were most popular in the war, this is one.'

Or:

'This is one of the [set:] {songs that were most popular in the war}.'

MrP
Comments  
Hello Aastha

I would say that the plural form is correct in all these cases. The antecedents here are mothers, songs, evils, and 'those'.

To test this answer:

'This is one of the songs that were most popular in the war'. =
'Of the songs that were most popular in the war, this is one.'

Or:

'This is one of the [set:] {songs that were most popular in the war}.'

MrP