A. <span>Exposure to an antigen
Exposure to viruses and antigens led to the foundation of modern vaccination. Vaccination introduces an antigenic material that helps the ability of the immune system to adapt a specific pathogen, therefore leading to a long-term immunity.</span>
The student is likely engaging or forming a hypothesis in which a hypothesis is a scientific method of having to formulate an intelligent or educated guess that may be an answer as to how a problem has occurred in which the student thinks that the racoon may live longer if it only eats vegetables.
Theories are a collection of scientific data that is generally accepted and reproducible. Theories are a result from several repeated experiments, but theories are not based on a single hypothesis. Several hypotheses are tested and appraised to become a well accepted theory. Theories may also be revised over time and can predict what may happen in the future. On the other hand, theories are not proven facts.
Answer:
An energy pyramid is a model that shows the flow of energy from one trophic level to the next along a food chain. The pyramid base contains producers—organisms that make their own food from inorganic substances. All other organisms in the pyramid are consumers
Explanation:
1st -When cells are small, the movement of food and waste can be efficiently handled by the cell membrane
