I'm not sure if what this question is asking but ill be assuming that the average molecular mass is required. An assuming that the abundance of each isotope is 50% the average molecular mass is 69.82 amu.
You can take two liquids of different densities (how much mass is in a given volume) and pour them into a funnel. An example is oil and water. When the mixture settles, the denser liquid will be at the bottom, and drips through the funnel first. This is a separation that you can just let occur naturally.
Answer:
<u>(A) Plants would probably not have enough nitrogen.</u>
Explanation:
<em>According to the passage, bacteria help us digest our food and make yogurt. But it is the bacteria in the soil specifically that "Cycle nitrogen through the ecosystem, which plants rely on"</em>