4. what must be true about an index fossil whose absolute age is used as a reference for other fossils?
the absolute age of the index fossil is actually unknown.
the absolute age of the index fossil was determined only by relative dating.
the absolute age of the index fossil was determined by radioactive dating or another absolute method.
the index fossils must be the same age as the other fossils.

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.