Question

complete the sentence.
snakes propel themselves along the ground with s-shaped movements, using both their ventral scales—which grip the ground like the tread on a tire—and ______.
by contracting their muscles
coordinated muscle contractions
submit
work it out
not feeling ready yet? these can help:
identify coordinating conjunctions
use parallel structure
use the correct pair of correlative c

Explanation:

The sentence uses the correlative conjunction "both...and..." which requires parallel structure. The first item after "both" is a noun phrase ("their ventral scales—which grip the ground like the tread on a tire"), so the second item after "and" must match this structure. "coordinated muscle contractions" is a noun phrase, while "by contracting their muscles" is a prepositional phrase, so the former maintains parallelism.

Answer:

coordinated muscle contractions