Apolar covenant bond is likely to form between two atoms that
a.) are similar in electronegativity
b.) are of similar size
c.) differ in electronegativity
d.) have the same number of electrons

A polar covalent bond is likely to form between 2 atoms that are C. Differ in electronegativity.

There is no reason to think the results are biased or not conducted properly but you should not assume the results are correct just because they were done in a laboratory so the answer would be c. it is likely to be reliable because the results support the conclusion presented.

Answerhund's rule;