True experimental designs (or randomized control trial) are considered strong designs because they have internal or external validity?

Which of the following is a form of hormone?

a. Tetracycline b. Aspirin c. Estrace d. Tylenol

Under NFPA classification, which of the following presents the most significant threat of producing ignitable vapors at ambient conditions?

A) Class IA B) Class IB C) Class IC D) Class II