Answer:
C. $5/1 lb
Explanation:
a unit price (= the price for one unit) is in this case (1 unit = 1 lb) the price for 1 lb of beef. 
we look in the graph at 1 lb (on the x-axis : the horizontal axis) and go up to the line and from there left to the y-axis (the vertical axis) and find $5 as price. 
so, the unit price is 
$5/1 lb