Which causes a drop in female hormone levels? the onset of the menstrual flow
the release of an egg from the ovary
the thickening of the uterine wall
the failure of an egg to be fertilized

Label the following as inner or outer planets; a) has 67 moons made mostly of hydrogen and helium b) has rings c)no moons, high volcanic activity d) known as the red planet, has 2 moons e) very thin atmosphere, moons or rings

Match the enzymes to their role in the dna replication process

Which factor is difficult to assess in a cost-benefit analysis