What was one reason the united states government gave subsidies and land grants to railroad companies in the 1800s?

The United States Congress wanted to create a "transcontinental railroad".

Explanation:

The Pacific Railroad Acts of 1862 was the way through which the United States Congress wanted to promote all aspects referring to the establishment of a "transcontinental railroad" throughout the United States. United States Congress wanted to accomplish this through the utilization of government bonds as well as the grants of the land regarding the different railroad companies.

In 1853, Congress authorized the War Department to conduct some surveys related to the five possible transcontinental routes. These routes would be from the north of Mississippi to the south. However, any route was established.  

d. the polar jet stream   lies between the polar easterlies and trade winds should be your answer