20) A standard passenger vehicle’s tires are required to have a minimum tread depth of...?

B) 1/16 inch and dont forget the age 10 years and it is past its used by date

Modern tyres have wear indicator bars, short webs of rubber spanning the tread groove at multiple points around each groove.

When the tread has reached these webs at any point, the tyre is considered unfit for use.

UK legal minimum is 1.6mm which is about 1/16 in, at which point the tyre is next to useless in rain .

Anything below 3mm (1/8) should be changed fairly soon.

Do I have to say it? Obviously the more tread the better. This is an old law. Guys use to have "Cheater Slicks" so they could burn rubber. There's no traction on a bald tire.

1/16. About the distance of the top of Ab Lincoln's head to the penny's rim.

Depends on the state you live in. 42 states consider 2/32 inch the minimum legal tread depth. California and Idaho consider 1/32 the minimum, and Arkansas, Montana, New Mexico, North Dakota, South Carolina and West Virginia have no standards on tread depth.

In my state, the answer is B.

Page 5 is the answer.

The book says 2/32 ... which is 1/16                              

1/16th of an inch or 2/32nds. Too thin for my taste. I always replace my tires when the tread gets down close to about 1/8th inch, +.

1/32 according to my husband