How can a reader make an inference about an author's unstated purpose? by determining the main topic of the passage
by taking a personal interest in the subject of the passage
by quoting a provable piece of information from the passage
O by making a reasonable guess based on information in the passage

D

Explanation:

it looks like the most reasonable answer, i give my apologies if this was incorrect/late

the american rail road was the most influential and useful transportation system developed in the 1800's with steam locomotives and in the very late 1800's and early 1900's diesel electric locomotives being used to transport goods and people around the newly expanded united states!