Much research is being done to increase the nitrogen-fixing ability of plants with root nodules. Why is this a

a). Decreasing the size of nodules will allow plants to fix more nitrogen into their own molecules.
b). By removing the bacteria from the root nodules, more fixed nitrogen will be available to the plants.
c).Increasing the nitrogen-fixing ability of plants will allow them to make better use of nitrogen fertilizers.
d). Nitrogen is an essential component of the amino acids used to form protein.

d). Nitrogen is an essential component of the amino acids used to form protein.

a). The size of nodules isn't an issue.
b). The bacteria are what fix the nitrogen or the convert atmospheric nitrogen into ammonia or nitrates.
c.) That isn't really logical. They could use nitrogen fertilizers just as easy for a source.