Potassium-40 has a half-life of 1.3 billion years. If a rock was determined to be around 3.9 billion years old what percentage
of the original potassium-40 would be left in that rock sample?

What is involved in redox reactions

Epinephrine is a hormone released from the adrenal gland of the body, most often in a stressful situation. it is known as the "fight-or-flight" hormone. one way that it causes a response in the body is to activate receptors on muscle cells. where are these cellular receptors located? a. on the cell membrane b. in the nucleus c. on the cell wall d. around the mitochondria

What makes a dominant allele different from a recessive allele