Nitrogen fixation, N2 --> NH3+, is not something that plants to by themselves but some plants have bacteria that does this. I believe that pea plants have these, but I'm not 100% sure.
<span>The correct answer is "Absorption of rainfall by soil."
The hyrdosphere refers to all water on the earth's surface. The geosphere, in this context, refers to the solid parts of the earth (rocks, sand, etc.) Since rain is part of the hydrosphere and soil is part of the geosphere, rain soaking into the soil would be an interaction between the two. The other choices deal with changes in the hyrdrosphere, but there is no interaction with the geosphere.</span>
<u><em>Naturally acquired active immunity:</em></u> It happens when someone is exposed to a live disease and gets the disease. The person then becomes immune as a result of the first immune response.
It's sort of like a fall and learn to get up for the body.
<em><u>Artificially acquired active immunity</u></em>: It can be isert into the body by a vaccine so you won't get sick. That's why if you get a flu shot, you won't get the flu, if you get a chicken pox vaccine, you won't get the chicken pox.
It's like you're body has a personal guide telling it where and where not to step in order to not fall.
