Which statement best explains why the United States grew into a world economic power in the 20th century?
A. The United States stayed out of major world wars and instead
made economic investments.
B. The United States put effective trade barriers in place to limit trade
with other nations.
C. The United States prevented other countries from abandoning the
gold standard
D. The United States increased its participation in international trade.

Most likely D

Explanation:

like many students at university, you may be unhappy about the results you attain in exams. you may feel that even with all you are doing there must be something more -- or different-- you could be doing to get better grades. we have all at some time or other heard of that student who only studies a couple of hours for final exams and scores a's every time. we stand in awe of those who seem to breeze through without undue effort and seem to need very little in the way of studying to nail an exam. the reasons for success, in what i think are the vast majority of cases, are less esoteric than many students think: successful students consistently apply a series of productive strategies with view to attaining clearly identified learning and grade goals throughout the academic term.