D. a viral disease because it is known and unknown and spreads.
They study the human body
Answer:
Active uptake (which I think you mean active transport) is important when the concentration gradient is against that of a certain substance, so it doesn't cross the membrane through diffusion or passive transport. It is sometimes necessary if a substance needs to move across a membrane but can't do so due to electrical charge or that there is a substance on the other side of the membrane preventing diffusion.
Explanation:
<span>Stress can lead to many dangerous diseases and puts unnecessary pressures o your body</span>
