That is the Sigma Symbol. It’s the addition of a sequence of numbers; the result is the sum of the total. if numbers are added sequentially from left to right, any intermediate result is a partial sum, prefix sum, or running total of the summation
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First one is D and Second one is B
Answer:
the soild material is allowe to settle into a sludge layer the remaining waste water undergoes a secondart treatment that uses bacteria to break down organic matter
treat water is left to sit while particles settle out, with settle d particles being added to sluudge,
water is disinfeted
Explanation:
