Answer:
I believe the answer is A
Explanation:
The other reasons would not give enough reason for competition between populations.
In your question have they given sammi's weaknesses?
In the experiment, the independent variable is the drug amount. Experiment group is given certain amount of drug, control group is not given the drug. The dependent variable is the body fat. I think you means the control is the living environment including food and water.
I’ve annotated your question and colour coded the answer, (the dotted line represents current bird population) and blue line represents what the population will look love after natural selection