Are these right? if not what are the answers?

Acceleration is a direct result of a.) balanced forces b.) unbalanced forces c.) gravity d.) velocity

What sentence best supports the statement that hormones are involved in the regulation of homeostasis? a. the hormone erythropoeitin increases the production of red blood cells when oxygen levels are low. b. the hormone oxytocin promotes labor contractions of the uterus during childbirth. c. the hormone melatonin induces sleep and its production is slowed by exposure to light. d. the hormone cortisol suppresses the immune system and is produced when the body is under stress.

Which of the following is the earliest era of earth's geologic time scale? cenozoic mesozoic precambrian paleozoic