D. Artificial selection. Think of French bulldogs as an example. They didn't exist from the start of time. Their ancestors were bred selectively to produce the desirable outcome.
Answer:Fixation - Fixation is the first step in the process of making nitrogen usable by plants. Here bacteria change nitrogen into ammonium. Nitrification - This is the process by which ammonium gets changed into nitrates by bacteria. Nitrates are what the plants can then absorb
