What is the maximum size for a postcard?

The correct choice indicates that the maximum size for a postcard is 4.25 x 6 inches. This size conforms to the United States Postal Service (USPS) requirements for postcards, which allows them to be mailed at the first-class postage rate without any additional surcharges.

Postcards must fit within specific dimensions to qualify for the lower postage rate. The specified size of 4.25 x 6 inches is both practical for mailing and a common format for many commercial and personal postcards, making it suitable for various user needs, including announcements, invitations, or marketing materials.

Sizes larger than this, such as those suggested by the other options, may exceed postal regulations or may require different postage if they cannot be classified as standard postcards. Thus, knowing the prescribed dimensions is essential for mailers to ensure their postcards can be sent efficiently and economically.