C. a memory aid
A mnemonic is a memory aid, usually a phrase or visual, that helps you remember a fact.
Frequency is the number of waves that pass<span> a </span>given point<span> in a certain </span>amount<span> of </span>time<span>. The frequency and wavelength of a </span>wave<span> are related. When frequency increases more </span>wave<span> crests </span>pass<span> a fixed </span>point<span> each second. hope this helps!
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Answer:
answer is 1
Explanation:
the reason for the crusades was to recapture Palestine from the Muslims and spread Christianity through Europe and the middle east
