The index of leading indicators is used to predict changes in business cycles. The correct option among all the options that are given in the question is the first option or option "a". It is basically used to predict the future of the upcoming economy. It can also be said that it does not always yield the perfect result.
Answer: 4- large-scale economic growth that resulted in the rise of big business
Explanation:
The Transcontinental Railroad allowed for goods to be transported across great distances and to previously inaccessible areas thereby increasing trade and contributing to economic growth. It led to the rise of the great and powerful Railroad companies.
The Bessemer process made it much more easier to produce steel and as a result led to the rise of the first business to be worth over a billion dollars in the US, the mighty US Steel. The increased volume of steel production aided economic growth as steel was a very sought after commodity.