Caffeine is also a what?
a. opioid
b. narcotic
c. barbiturate
d. psychoactive

Which of the following is the sl unit used to measure temperature a. kilogram b. liter c. meter d. kelvin

On a spring day, a middle-latitude city (about 40? north latitude) has a surface (sea-level) temperature of 10 ? c. if vertical soundings reveal a nearly constant environmental lapse rate of 6.5 ? c per kilometer and a temperature at the tropopause of –55 ? c, what is the height of the tropopause?

What characteristic makes a cell membrane selectively permeable