Answer:
84 mm (C)
Explanation:
We are given the centimeter/millimeter side of the ruler. It is probably easier to first look at the centimeters since the lines are much bigger. We can see that the line goes from 0cm to around 8.4cm. Now, we can convert centimeters to millimeters because we know that there are 10 millimeters in one centimeter. 8.4cm * 10 gives us 84 millimeters (C)