Space Trips Inc. files a registration statement with the SEC before making an offering to the general public. The registration contains false, immaterial statements of which the investors are unaware. Space Trips is charged with violating the Securities Act of 1933. Space Trips's best defense is

a. the investors were not aware of the misrepresentations.
b. the issuer reasonably believed the misstatements were true.
c. the offering was made available to the general public.
d. the untrue statements were not material.