A box plot is made up of five numbers, also known as the five number summary: min, Q1, med, Q3, max. Q1 and Q3 can be found by looking at the lines one space out from the middle, making up the outside of the box.
To find the IQR, we need to subtract Q1 from Q3.
A: 70 - 60 = 10
B: 85 - 60 = 25
C: 80 - 70 = 10
D: 75 - 65 = 10
The box plot with the largest IQR is B.
Hope this helps!! :)
