How do vaccines work? A. They activate your immune system so that it is fighting all the pathogens that are in the
environment currently
B. They expose the immune system to a weakened or dead version of a pathogen so that
the body can build a memory of the pathogen to fight future infections.
C. They help the body fight off all the strains of one particular virus
D. They kill viruses that are currently living in the body

when you breathe in, or inhale, your diaphragm contracts (tightens) and moves downward. this increases the space in your chest cavity, into which your lungs expand. the intercostal muscles between your ribs also enlarge the chest cavity. they contract to pull your rib cage both upward and outward when you inhale.

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the rocks are classified by the geological process they are formed by. the three main groups of rocks are igneous, metamorphic, and sedimentary. minerals are not they are classified under the chemical classes they are in. these groups include silicates, sulfates and carbonates.