Why does your leg bruised if you get hurt?

A bruise, or contusion, appears on the skin due to trauma. Examples of trauma are a cut or a blow to an area of the body. The injury causes tiny blood vessels called capillaries to burst. Blood gets trapped below the skin's surface, which causes a bruise.

c.) polymerase chain reaction

- "unlike the original dna fingerprinting method, dna profiling does not use restriction enzymes to cut the dna. instead it uses the polymerase chain reaction (pcr)? to produce many copies of specific str sequences. pcr is an automated procedure that generates lots of copies of a specific sequence of dna."

b - the respond is innate and varies over time.

good luck!