Detailed Answer
Answer (A) is correct.
Reasonable assurance is provided when cost-effective actions are taken
to restrict deviations to a tolerable level. This implies, for example, that
material errors and improper or illegal acts will be prevented or detected
and corrected within a timely period by employees in the normal course
of performing their assigned duties. The cost-benefit relationship is
considered by management during the design of systems. The potential
loss associated with any exposure or risk is weighed against the cost to
control it.