Explanation:

- Risk of over-reliance: This occurs when auditors rely too much on controls, potentially overlooking misstatements. If the controls are not effective, it can significantly impact the audit's effectiveness.

- Risk of incorrect rejection: This happens when auditors wrongly determine that a balance or control is incorrect. It doesn't affect the effectiveness directly but may lead to unnecessary additional audit work.

- Risk of incorrect acceptance: This is when auditors accept a balance or control as correct when it is not. It can result in not detecting material misstatements, hence affecting audit effectiveness.

- Both (a) and (c): As both these risks directly impact the precision and accuracy of the audit outcomes, they both affect the audit’s effectiveness.