What Impact Did the End of Roman Expansion Have on the Economy

What impact did the end of Roman expansion have on the economy of the empire?

A) It permitted the empire to focus its resources over a smaller territory and reduced the strain on the imperial economy.
B) The primary result was the restriction of Roman commerce to trade with sub-Saharan Africa.
C) The economy suffered as the Romans lost control over the trade of the Indian Ocean.
D) The end of expansion led to a labor shortage as the Roman economy depended on a steady supply of slave labor.