OPEC means Organization of Petroleum Exporting Countries, which is a group of oil producing countries that regulate the amount of oil each country is able to produce. An example of OPEC members are Saudi Arabia, Iran and Iraq.
(A) He may have acted alone, although Austria-Hungary thought he was helped along by the Serbian government. ... (C) He was probably assisted by the Serbian government, which hoped that his actions would spark a world war and help Serbia gain independence.
Four of those inventions were, The hot air balloon, the light bulb, mayonnaise and the piano. (: Hope this helps!