Final answer:
Significant deficiencies and material weaknesses must be communicated to an entity's audit committee because they represent risks and vulnerabilities in the entity's internal control over financial reporting.
Step-by-step explanation:
Significant deficiencies and material weaknesses must be communicated to an entity's audit committee because they represent risks and vulnerabilities in the entity's internal control over financial reporting. These deficiencies and weaknesses can result in material misstatements or inaccuracies in the entity's financial statements, which can have serious consequences for shareholders, investors, and other stakeholders.