Answer:
Explanation:
- The Grand Canyon, 277 miles long and 18 miles wide, was formed by the Colorado River.
This sentence is divided in-to two parts that need to be separated by two commas. So, it is necessary to use two commas and not one.
<u>The two parts are;</u>
- The Grand Canyon was formed by the Colorado River. (clause)
- 277 miles long and 18 miles wide. (phrase)
A phrase always add more information about the clause and is nothing without it. To incorporate the phrase into the clause in the middle, we must use two commas to make the sentence and the phrase and clause more visible and understandable!