20. Rome was able to conquer so much territory due to all of the following EXCEPT for: a strong and disciplined army
a well developed education system
allowed conquered people to become citizens
allowed conquered cities to keep their customs and traditions

Would be B.

Explanation:

The Roman Empire's schooling wasn't at all advanced, it was only offered to the rich. Hence, the majority of the population didn't receive education, so it couldn't have helped their military.

increasing defense spending.

explanation:

i confess that there are several parts of this constitution which i do not at present approve, but i am not sure i shall never approve them: for having lived long, i have experienced many instances of being obliged by better information or fuller consideration, to change opinions even on important subjects, which i once thought right, but found to be otherwise. it is therefore that the older i grow, the more apt i am to doubt my own judgment, and to pay more respect to the judgment of others.