Which of the following statements concerning evidential matter is correct?

a.A client's accounting data cannot be considered sufficient audit evidence to support the financial statements.

b. An effective internal control structure contributes little to the reliability of the evidence created within the entity.

c. The cost of obtaining evidence is not an important consideration to an auditor in deciding what evidence should be obtained.

d. Competent evidence supporting management's assertions should be convincing rather than merely persuasive.