Clinical trials for drugs include
a. animal testing.
b. human testing only.
c. tests on cell cultures.
d. human testing and a comparison test with existing drugs.

Explain why methicillin resistant staphlococcus aureus (mrsa) is more prevalent now than it was only 30 years ago. a. antibiotics cause mutations in staphlococcus aureus that lead to an increase in the number of methicillin-resistant strains. b. methicillin resistance causes an infection to spread more rapidly.c. frequent and inappropriate use of methicillin-type antibiotics has provided selective pressure that has resulted in an increase in the proportion of methicillin-resistant strains of staphlococcus aureus.d. diseases like aids have made people more vulnerable to infections from staphlococcus aureus.