Passive transport is characterized bya. the expenditure of atpb. no use of energyc. movement of molecules from a low concentration to a high concentrationd. movement of molecules from a high concentration to a low concentratione. a and cf. b and d

Where do the respiratory and circulatory systems meet? a. in the heart b. in the muscles c. in the lungs d. in the brain

Hairs that clean dirt out of the air in your nasal passages are called: a. sinus b. trachea c. cilia d. mucus

Crinoids, also known as sea lilies, appear to be sea plants but are not plants at all. crinoids are an echinoderm species which uses anchoring structures called holdfasts to attach themselves to the sea floor. crinoids were most abundant in pennsylvania during the mississippian period, which ranged from 375 to 320 million years ago. fossils of the crinoids shows that during most of this time pennsylvania was that provided favorable conditions for crinoid growth. a) glacial terrain b) a dry and sandy plain c) mostly mountain ranges d) covered by warm, shallow seas