Answer: B) $3.00 for every pound
I'm assuming there should be a dollar sign here. This is the same as saying "$3 for one pound". A unit rate has some amount per 1 unit of something else. In this case, the 1 unit is 1 pound.
A different example of a unit rate is writing 40 miles per hour. This is the same as saying the car drives 40 miles in 1 hour. The unit here is the "1 hour".