Question

The repetition of similar grammatical structures in a poem is

meter.
iamb.
parallelism.
antithesis.

Answer 1

Parallelism because you use the same structures over and over

Answer 2

The repetition of similar grammatical structures in a poem is parallelism!

Parallelism is defined as the use of verbal constructions in poetry that correspond in grammatical structure, sound, meter, meaning, etc.

Hopefully this helps!