Which of the following best describes a properly controlled experiment

This is so important ugh its 25 points

Under the soviet system, the government a. controlled all forms of communication. b. allowed newspapers to print whatever they wanted. c. controlled editorials but not the reporting of news. d. encouraged access to a wide variety of news sources. select the best answer from the choices provided a b c d

Which short-term environmental change is most likely to lead to ground shifting, landslides, and the collapse of buildings or roads? forest fires flooding earthquakes