Which of the following is considered a xanthine?
a. acetylcysteine
b. guaifenesin
c. theophylline
d. epinephrine hcl

What protects the lining of the stomach from acidic gastric juices?

What evidence did mendel find that supported his law of independent assortment? a. some traits are controlled by several different genes. b. a trait can be passed on from a parent to an offspring. c. most traits have a dominant form and a recessive form. d. different traits are passed on independently of each other.

Natural selection changes allele frequencies because some survive and reproduce more successfully than others.