Affordability and climate
<span>Magnetic declination is the angle between magnetic north (the direction the north end of a compass needle points) and true north. The declination is positive when the magnetic north is east of true north. The term magnetic variation is a synonym, and is more often used in navigation. Isogonic lines are where the declination has the same value</span>
Nucleus of the atom, that contains protons and neutrons.
One could argue that photosynthesis is the most important chemical reaction of all, since it makes energy from solar energy. Plants are are at the bottom of most food chains, and you get O2 as a side product, which a lot of organisms rely on for respiration and for other chemical reactions.
I hope this helps. I'm not sure if the "passage" has any additional information since you didn't attach it.