Question

Read the sentence. In the early 1800s, coal mines west of Philadelphia provided a huge fuel supply, and industries thrived in the city.
Which revision corrects the faulty coordination in the sentence?

A. In Philadelphia in the early 1800s, industries thrived because coal mines west of the city provided a huge fuel supply.
B.Philadelphia industries thriving during the early 1800s, but coal mines west of the city provided a huge fuel supply.
C. In the early 1800s, industries thrived in Philadelphia, and coal mines west of the city provided a huge fuel supply.
D. Although Philadelphia industry thrived during the early 1800s, coal mines west of the city produced a huge fuel supply.

Answer 1

A) In Philadelphia in the early 1800s, industries thrived because coal mines west of the city provided a huge fuel supply (I physically took the quiz and selected "a" and I got the question right.

Answer 2

A. In Philadelphia in the early 1800s, industries thrived because coal mines west of the city provided a huge fuel supply.

The original sentence does not show that the coal helped the industries thrive. The revision must show the connection between the two ideas: the city thriving and the huge fuel supply. Option B uses the conjunction but which indicates a contradiction. This does not work. Option C simply states that both ideas occurred in the 1800s. Option D uses the transition word although which is a concession. Neither idea is conceding to the other.