Answer:
Measuring a pencil in meters would be very difficult, as a single meter is much longer than one pencil. Also, measuring a hallway in millimeters would be very difficult considering how small millimeters are in comparison to a hallway. However, if you switch these two then they would work very well.
The second one, I could be mistaken though
Answer:
This question sadly does not make much sense, please rephrase it.
A. Industrial pollution, the rest are considered positive