Why are there hundreds of different protein channels?
a. they work for different molecules
b. the cells make multiple protein channels just in case one dies
c. in case molecules have to go from a low to high concentration
d. smaller molecules will go through protein channels to save space

I think that the answer is A

I'm not 100% sure though sorry. Hope this helps.

the "dirty dozen" chemicals banned in an international treaty are formally known as persistent organic pollutants, or pops. the united nations environment program provided this background on what they are and what they can do to humans and wildlife.

i hope this

there really is life in the deepest part