I think compound because there were no dependent/independent clauses.
The 1920's was a time of sensational economic growth and progress. Mass produced goods such as clothing, radios and cars were in abundance. The stock market boomed and most Americans benefited. But there was also economic inequality, thus the prosperity of the 1920's was unsustainable.
A: terribly: modifies old, an adjective
B: very smart: very modifies smart, an adjective
C; extremely modifies "slow", an adjective again
D: quickly modifies "hid" a verb - this is the correct answer!
