17. what's mass?
a. a measure of an element's attraction for electrons
b. the force that gravity exerts upon an object
c. the sum of the number of protons and neutrons in an atom
d. a measure of the amount of matter an object contains

The force that gravity exerts upon an object.

on the planet jupiter, the acceleration due to gravity is approximately 26 m s2 , roughly 2.7 times the acceleration due

the solute can move "downhill," from regions of higher to lower concentration, relying on the specificity of the protein carrier to pass through the membrane. this process is called passive transport or facilitated diffusion, and does not require energy.