Take another look at the sentence:

The hike through the canyon exhausted Kim. The steep incline made her thigh muscles throb, __________, and the relentless sun burned her skin.

The blank requires a short main clause. You chose shoulders that ached from the heavy pack, which is a noun followed by a relative clause. You thus have a parallelism error.

Before you continue, review the rules for parallel structure.

Go back to the sentence to try again.

HomeTermsExercises MOOCHandoutsPresentationsVideosRulesAboutShopFeedback