Answer:
Parsec equal to about 3.26 light years.
Explanation:
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Description
DescriptionReflection is the change in direction of a wavefront at an interface between two different media so that the wavefront returns into the medium from which it originated. Common examples include the reflection of light, sound and water waves
<span>E. Stimulation of T-cell by APC</span>
The initial exposure of the body to an infectious agent e.g. through a vaccine, triggers an immune response most of which rapidly diminishes after the vaccination. However some cells of the immune system called lymphocytes remain with a memory of that pathogen.As a result, if the same pathogen infects a vaccinated person, the memory cells remember and recognize it and rapidly spring into action triggering a much more rapid response specific to that pathogen than the initial exposure, effectively dealing and neutralizing the pathogen.
