A control deficiency would be considered a material weakness when the likelihood that potential financial statement misstatements will not be prevented, or detected/corrected, and the magnitude of such misstatements are at a minimum:
Choice "C" is correct. A material weakness is a deficiency, or combination of deficiencies, such that there is a reasonable possibility that a material misstatement of the entity's financial statements will not be prevented or detected/corrected.
Choices "b", "d", and "a" are incorrect, based on the explanation above.
