Read the following excerpt from "Andrew Carnegie: An American Philanthropist" and answer the question below.

"Carnegie was thirteen years old when he began his first job in Allegheny, Pennsylvania. He worked as a bobbin boy for $1.20 a week. Next, he was employed as a messenger for a local telegraph company. While he was working as a messenger, Carnegie taught himself how to send and receive messages using the telegraph equipment. His motivation and dedication won him the position of private secretary and personal telegrapher for the superintendent of the Pittsburgh division of the Pennsylvania Railroad. This position put Carnegie in the sights of Thomas A. Scott, the superintendent of the entire Pennsylvania Railroad. Scott offered Carnegie a job. In addition to the job, Scott introduced Carnegie to the investment world and set up his first investment with the Adams Express Company. Three years later, Carnegie himself became superintendent."

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What is the main idea of this passage?
A. Carnegie eventually replaced the man who hired him.
B. Carnegie began working at a very young age for a very low wage.
C. Carnegie's hard work and desire to learn led to his rapid success in business.
D. The fact that Carnegie was the personal secretary of the superintendent of the Pittsburgh branch of Pennsylvania Railroad caused him to come to the attention of Thomas A. Scott.