Which of the following statements about the Securities Act of 1933 is not true?

a. Third parties must prove that the auditor was guilty of negligence.

b. Third parties' prima facie case is an alleged false statement or misleading omission in the audited financial statements

c. Third parties do not have to prove that their investment losses were caused by the false statement or misleading omission in the audited financial statements.

d. The auditor's potential liability extends to the effective date of the registration statement.