D. it clearly connects ideas
Parallelism is when the same grammatical or sentence structure is used for a list of ideas or items. By using a similar grammatical structure the reader's brain automatically makes a connection between the ideas because of the similar structure. Caesar's famous line "I came. I saw. I conquered." is an example of parallelism. Each of the sentences has the format subject-past tense verb.
To decrease the size in population.
I think that its A because B and C doesn't make sense and D has nothing to do with the topic.
A nexus is the series of connections linked together. A redux means brought back, or revived.
Hope this helps!!!:)