Finding Grammatical Error In A Model SAT sentence [closed]
The easiest way to check this sentence is to remove the qualifiers and see what the core says:
Sacajawea, a Native American woman, whose ability to translate between indigenous languages and English was extremely helpful to the explorers, Louis and Clark, on their expedition to the Pacific Ocean.
At this point it's now clear that there's no verb associated with "Sacajawea", which is the grammatical error.
Sacajawea, whose ability was helpful.