<span>d. the air heats and expands rapidly.</span>
Answer:
Competition.
Explanation:
Competition refers to a relationship between rival organisms whose economic niches overlap with each other. When both organisms compete with each other for the limited resources available in ecosystem.
In the given case, the Sparrows replacing Bluebirds is a result of competition. Because they both share the same ecological niche, they are in competition with each other for the limited resources.
Therefore, competition is the correct answer.
It will take 4 years because you need a bachelor's degree and a state licence to teach in a public high school.
Unless I am missing some very specific context for this; this is false, Romania does not share a border with the United States, much less a ground border. Romanians would have to take a ship or a plane to go to the US.