which one is grammatically correct?

"one of the main topics
was
the
parts of..."
or
"one of the main topics
were
the parts of..."

Anonymous2021-04-06T14:33:21Z

ONE [of the main topics] WAS the parts  .  .  .

The verb agrees with the subject, not with the predicate noun.

busterwasmycat2021-04-05T14:37:59Z

one was. and always will be.

robert20202021-04-05T10:35:39Z

Was. The topic was singled out. ONE of the main topics 'was'.....

geezer2021-04-05T08:05:56Z

''ONE of the main topics WAS'' .... Singular
It would be ..
''The main topics WERE'' ............. Plural

OTTO2021-04-05T08:05:19Z

Was/were refers to "one." Therefore the answer is "was" ( one was, not one were).