HELP PLEASE Which of the following is a good description of biological clocks?
a) A light-dark cycle of 24 hours during which entrainment takes place
b) External chemical systems that are regulated by time and control circadian rhythms c) None of these
d) Internal chemical systems that are regulated by nature and control parts of the body

Penelope studies how the structure and function of the nervous system is related to behavior. she is a psychologist

Grade 91.)the gravitational pull from the moon words).2.) what is the rate of gravitational 3.)if you drop a hammer, is it more likely to drop handle side down, head side down, or equal chance that it will land either way? why? 4.)a car moves 60km east and 90km west.a.) what is the distance the car traveled? b.) what is the car's displacement5.)what is the average velocity of a car that moved 60 km south in 3 hours? 6.) a car starts from rest and acceleration to 60 m/s over a time of 5 seconds. what is the acceleration of the car? 7.)what is the speed of an object at rest?

How far down have geologists drilled holes ? (science) a: 3.8 km b: 12 km c: 100 m d: 1200 km