Progesterone is a hormone released by the corpus luteum in the ovary. It plays important roles in the menstrual cycle and in maintaining the early stages of pregnancy. It may also be involved in the growth of certain cancers.
I've been following various people's posts about the GRE for 10 months now. Some people don't study at all for the GRE, some study for a weekend, the average is about 2 to 3 months, and some study for a year or more.
Some schools may also require you to take one or more GRE Subject Tests. The purpose of each GRE examination, of course, is to help graduate schools decide if you've got the right stuff for their program. Important Note: The GRE Test changed recently, on August 1st, 2011.