A “double blind study” in which the researchers themselves do not even know which group is the placebo group and which group is a medicated group is more accurate than one in which the researchers know what the participants are getting. Why?

Which of the following natural processes is most likely to support the formation of an underwater sinkhole? a pollution buildup from deposited minerals b limestone cave collapsing due to changes in sea level c erosion of large amounts of sand moved by ocean waves d oxidation of rock formed by chemical weathering