Answer:
A. It will show whether the changes observed in group 1 depend on the metabolic activity of soil bacteria.
Step-by-step explanation:
The seedlings in group 1 will be treated with a solution that contains actively reproducing bacteria, which will be metabolically active. In contrast, the seedlings in group 2 will be treated with a solution that contains heat-killed bacteria, which will be metabolically inactive. The researcher will be able to compare the results for group 1 with those for group 2. The comparison will help the researcher determine whether the changes observed in group 1 depend on the metabolic activity of soil bacteria.
I also got this question correct so I am sure.