The correct answer is 26. To determine the correct highway to travel on, you need to have some geographical knowledge or have access to a map or navigation application. In this case, you would need to understand that Greenville and Charleston are both cities in the state of South Carolina, USA. By looking at a map of South Carolina, you will see that the most direct highway connecting Greenville to Charleston is Interstate 26 (abbreviated as I-26). Hence, I-26 is the correct highway to travel on for the route from Greenville to Charleston.
