Thirty patients with acne volunteer to be treated with either a medicinal lotion
or a normal moisturizing cream. this type of experimental design is called
a(n)
a. in vitro observation
b. clinical trial
c. geographical cohort study
d. general population survey

Thirty patients with acne volunteer to be treated with either a medicinal lotion

or a normal moisturizing cream. This type of experimental design is called

a clinical trial.-B.

one characteristic that is shared by all is a soft body. many

of these invertebrate animals also have an outer shell to protect their

body. oysters, clams, snails, and mussels are all mollusks. so are octopuses, squids, and slugs. mollusks live on land and in freshwater.

the answer is "a.) well–developed vascular system."

explanation: