Answer:
The biologist is studying about the ecological community.
Explanation:
The ecological community refers to the community in which population of different types of species survives together. As the biologist is observing about the interaction of different populations of Pennsylvania region, it can be inferred that the he is studying about the ecological community of Pennsylvania region.
The population surving in the community interact with each other through different modes of interaction. It may either parasitic, or mutual, or competitive or predication or commercialism.
Answer:B.
It was used to prove that smoking causes health problems.
Explanation:
Answer:
It releases carbon dioxide and decreases Earth's supply of oxygen. It absorbs oxygen, thus decreasing Earth's oxygen supply
Explanation: