Which sentence contains parallel structure?

a.) mekhi was finally finished with his chemistry homework.
b.) mekhi finished his chemistry homework before basketball practice.
c.) mekhi spent three hours finishing his chemistry homework.
d.) mekhi finished his chemistry homework and then finished his essay.

The correct answer is D. Mekhi finished his chemistry homework and then finished his essay

Explanation:

In grammar, parallelism refers to the repetition of the same grammatical pattern or structure that creates a parallel or balance between the elements of a sentence by presenting them in the same way. This means when there is parallelism more than one element in the sentence has the same grammatical structure, this is used to make the sentence concise and easy to read and understand. Considering this, the sentence that contains parallel structure is "Mekhi finished his chemistry homework and then finished his essay" because in this sentence the two tasks Mekhi finished are presented using the same grammatical structure which is composed of the verb in past "finished", followed by the possessive pronoun "his" and followed by a noun that works as an object "homework" or "essay".

the answer should be d) he was one of those young thousands who greeted the war with a certain amount of relief, welcoming the liberation from webs of tangled emotion" since it is the best option because it shows his desire to free himself. 

hope this answer you! have a great day.