Three students measured the height of a lab table each using a different meter stick. one student reported a height of 98cm, another reported a height of 70 cm. the most likely explanation for the difference in the reported heights is that one

The difference between the two students that we know of is that they used a different meter stick. So the difference would be best attributed to  the different tools they used.

Note, this is quite a huge difference. It's likely that one of the sticks, or both, are quite defect.