Rome faced constant attack after the pax romana because its army was becoming less loyal to the emperor. was becoming more loyal to the emperor. had trouble paying mercenaries to fight. had trouble finding mercenaries to fight.

Rome faced constant attack after the Pax Romana because its army "was becoming less loyal to the emperor". This was mainly because Rome had been at peace for so long the soldiers did not have as much incentive to fight on demand. 

C is the correct option.

Explanation:

Trade blocs are intergovernmental agreements and can be part of a regional intergovernmental organization where trade barriers are reduced and eliminated among the participating countries. Trade Blocs are also the only agreements between different states. It can also be a part of regional organizations. They can be classified based on the level of economic integration into Preferential trading partners, custom unions, and common markets. Some examples of trade blocs are NAFTA(North American Free Trade Union) and ASEAN (Association for South East Asian Nations).