Which statement best describes a challenge in the Roman economy?

The tax burden on citizens in Rome was too high

Explanation:

If your options are the following:

Rome had difficulty finding trading partners

Rome lacked resources to build infrastructure

The tax burden on citizens in Rome was too high

Trade competition led to conflict between social classes

The answer is The tax burden on citizens in Rome was too high. Rome had plenty of trade partners, was renowned for its infrastructure, and while there certainly were some conflicts between social classes, taxes were a far greater contributing factor to the fall of the empire, and thus are a better option for the question.