Trade routes in the 1500s were probably easier and faster when the routes 1) where entirely over land
2) included water when possible
3) went farther north
4) passed through constantinople

2) included water when possible

Explanation:

During the period of 1500s traveling on trade routes or any routes are either through land or water. Given that, at this period, traveling on land for a long distance will typically be donkeys with coaches. While that of water will be on the ship. Thus, comparing the speed and the ability to move without stopping for rest, it can be concluded that trade routes in the 1500s were probably easier and faster when the routes "included water when possible."

d is the best answer for this question.