involves mainly T cells and leads to the destruction of cells that are infected with viruses 2. involves mainly B cells and takes place in blood and lymph 3. being able to resist a pathogen that infected the body in the past 4. the deliberate exposure of a person to a pathogen in order to provoke an immune response 5. part of the immune system that produces lymphocytes 6. results when antibodies are transferred to a person who has never been exposed to the pathogen 7. the third line of de

Bacteria have complex internal structures.

The scientific method is a series of steps followed by scientific investigators to answer specific questions about the natural world. it involves making observations, formulating a hypothesis, and conducting scientific experiments.the steps of the scientific method are •observation-the first step of the scientific method involves making an observation about something that interests you•question-once you've made your observation, you must formulate a question about what you have observed. •hypothesis-once you've made your observation, you must formulate a question about what you have observed. •experiment-once you've developed a hypothesis, you must design and conduct an experiment that will test it.•results-the results are where you report what happened in the experiment. •conclusion-the final step of the scientific method is developing a conclusion.i hope that this you : )

Ithink the answer is d.