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A is corrent because a system of quality control is necessary to provide a CPA firm with reasonable assurance that it is conforming to generally accepted auditing standards.
B is incorrect because a system of quality control is necessary to provide the CPA firm with reasonable assurance that it is conforming to professional standards. Continuing professional education is only a part of a firm’s system of quality control.
C is incorrect because a system of quality control is necessary to provide the CPA firm with reasonable assurance that it is conforming to professional standards. A system of peer review is only a part of a firm’s system of quality control.
D is incorrect because it relates only to reporting standards.