If the real GDP is less than the equilibrium GDP, it suggests that the economy is operating below its potential output, often resulting in increases in inventories and downward pressure on prices. The adjustments that the economy would go through to achieve equilibrium GDP could involve changes in both prices and production.
In this scenario, the correct adjustment would be:
Competition among consumers will increase the price level, encouraging firms to produce more.
This option correctly highlights that as consumers compete for a limited number of goods, their willingness to pay may drive prices up, which in turn will incentivize producers to increase output to meet the higher demand.