Answer:
D) The Soviet economy was a tremendous success story; the USSR would still be together if it were not for the ethnic differences.
Explanation:
The Soviet economy was not a tremendous success, in fact, it was in many aspects a failure (although it was a success in some fields).
The other 3, true statements in the question give us a clue why:
The Soviet system benefited the center (Russia) disproportionally, leaving aside the other, peripheral republics in Central Asia, the Caucasus, The Baltics, and Eastern Europe, which were often very poor.
The Soviet system used a planned economy, instead of a market economy, and this led to many errors in the production of goods and services. Resources were often poured in unprofitable industries over more profitable ones, and the geographical location of the economic sectors often did not make sense.
Things that in a market system would likely not happen, ocurred in the soviet planned economy because the planners did not realize their mistakes.
