Biodiversity is valuable partly because it:
a. gives us interesting things to look at.
b. tells us about many other species..
c. contributes to medicine and agriculture..
d. provides humans with resistance to disease..

i think that d. wind is the answer.   i missed the question when i answered a. currents.

hydrogen is a compound or a single element and a element is a pure substence that cannot be separated into simpler subtances

clorine is a compound its a chemical substance that forms when two or more different elements combine

so both hydrogen and clorine are compounds