A researcher is interested in the effects of a vegetarian diet on memory. One group eats a strict vegetarian diet for three months, a second group eats a strict vegan diet for three months, while a third group eats anything they want for three months. After three months, all participants are given a memory test. Results indicated that memory was is better for both the vegetarian and vegan groups. In this study, the independent variable is:

In the kingdom of saudi arabia the government controls every aspect of oil production which makes up the majority of the country's economy. while other businesses are owned by individuals, the biggest segment of saudi arabia's economy is oil production. saudi arabia's economy would best be described as a) entirely market. b) almost entirely command. c) a mixture between just market and traditional. d) a mixed economy with large amounts of command.