Answer: Hello there!
We know that the ruler has centimeter and inch markings.
First, analyze each option:
A: 2.85 mm
This is a really exact measure in mm, but the ruler has markings in centimeters, then you can divide each centimeter into 10 marks of 1 millimeter each, and you can measure millimeters with it, but you cant measure a 0.85 of a millimeter with it (maybe 0.5, but no more precise than that), then this measure is not possible to do whit this type of ruler
B = 3.0 inches
If the ruler has inches as units, this is a possible result in the lecture, but is a really thik cardboard piece, so is not likely to be the answer.
C: 0.118 inches
again, this is a very exact number, you can expect to have a lecture of 0.1 inches or 0.2 inches, but not one with that many significant numbers after the decimal point.
D: 3.0mm
This is equivalent to the A measure, but rounded up, is a less exact measure because you don't have significant numbers after the decimal point. Again, if you divide the centimeter into 10 marks, you can measure 2 mm or 3 mm (or 2,5 mm if you look in between both marks) but not a number as exact as 2.85mm, then this lecture makes more sense.
Then the possible answers are D and B, where B requires a really weird and thick piece of cardboard but is a possible measure.