7.
(A) If both and m are abolitely cnvergemt, than
(B) If is convergent and is divergent, then must be divengent.
(C)Sugpose that f(x) is a positive and continuous function on [1,∞), and the improper integral

f(x) de is convergent. Let a_n = f(n), then a_n is convergent.

n=1
(D) Ifa_n≤ b_n for all n is convergent, thena_n must be convergent.  

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