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.
I believe the answer is A.
Answer: For 1 mole of a single atom it is equal to its molar mass. And a single atom, 1 mole is equal to the Avogadro's Number.
Explanation: The relationship can be expressed through the following:
1 mole = molar mass of an atom/ compound
1 atom x 1 mole / 6.022x10^23 atoms