1. mike injured his knee while playing. examination revealed that the injured area was red, swollen, and warmer than the surrounding area. what does this condition indicate?

an inflammation

a tumor–like growth

a hemorrhage

2. when a virus invades the body, some b cells recognize it as nonself and produce plasma cells that release a substance to kill the virus. what is this substance called?

antigen

antibody

pathogen

3. which of the following forms blood clots?

fibrin

macrophages

thrombin

4. an antigen has invaded a mammal's body. specific immune cells engulf and ingest it. some of the digested pieces are displayed on the cells' bodies. what happens next?

b cells are activated and release antibodies.

t cells are activated and produce clones.

b cells withdraw the immune response as the antigen is killed.