The length of time required for half of the radioactive atoms in a sample to decay is its
a. half-life.
b. relative date.
c. radioactive date.
d. period.

In the practice of science, this type of reasoning is used to develop explanations.

Which pair of sentences is describing the same velocity? a. a car is parked. a car is moving in circles. b. a bus drives 40 miles per hour north. a truck drives 50 miles per hour north. c. a boy walks east at 6 kilometers per hour. a girl walks west at the same speed as the boy. d. valerie rides her bike south at 8 kilometers per hour. owen jogs south at 8 kilometers per hour.

Agland that serves both the digestive and the endocrine systems is called