The purpose of the Columbia Canal was to

The Columbia Canal is the surviving canal of a series of canals built by the State of South Carolina in 1824 using the labor of indentured Irishmen to provide direct water routes between the upstate settlements and the towns on the Fall Line

Explanation:

the answer for 3 is b and the answer for 4 is d

answer: the time zones used to be whatever the local authority wanted them to be. one town might have 6am whenever the sun came up and another town had 6am 10 minutes later.  

the trains had a hard time when their orders said to be at a certain point at 6am.  

6am, but who's 6am.  

the railroads got together and set the time zones more or less along the longitude lines across the country.

explanation: