What is a concentration gradient? what does it mean if a molecule diffuses down it's concentration gradient?

Which must be kept in mind when determining if an explanation is correct? check all that apply. which must be kept in mind when determining if an explanation is correct? check all that apply.

How do water’s relative densities as a solid and a liquid differ from that of most other substances? water’s solid and liquid forms have different densities, while most other substances have solid and liquid forms with similar densities. water’s solid and liquid forms have similar densities, while most other substances have solid and liquid forms with different densities. water’s liquid form is less dense than its solid form, while the opposite is true of most other substances. water’s solid form is less dense than its liquid form, while the opposite is true of most other substances.

What determines whether a particular cell is able to respond to a hormone?