When checking your tires, which of the following is not an issue to correct?

Problems to check for when inspecting tires include: air pressure that is too low or too high; using radial and bias-ply tires together; tread depth of less than 4/32 of an inch in major grooves on front tires; and tread depth of less than 2/32 of an inch on all other tires.
DMV Writen Test