1 yard = 3 feet
Divide 34 by 3, you should get 11 and 1/3.
So the classroom is 11 1/3 yards long, but 1/3 of a yard just so happens to be one foot, as 3 feet is 1 yard.
That means that the classroom is 11 yards and 1 foot long, or answer choice B.
Hope this helps! :)