Judging by the map, which best explains why the empire’s western half was hard to rule? The west suffered economically because it did not have adequate ports. The west covered a large territory and was at more risk of foreign invasion. The west had a more diverse population because it bordered three countries. The west did not have enough troops to protect its vast amount of territory. ANSWER b

The answer is "second choice"

Explanation:

For a successful rule, the Empire of Rome was becoming too huge and the external regions do anything they want. They were trying to find a way to solve this and other issues. He concluded that breaking Europe into two parts would be the solution.  

In this question, Whenever we see the map, it explains that perhaps the west contained a vast area but was at higher risk of foreign occupation, that's why the western half of the kingdom was difficult to control.

a.) are both appointed for life