Everything but C has a saddened tone to it because it shows a bit of pity or jealousy towards some of the sentences.
Gladwell has a few different arguments to make regarding Asian excellence at mathematics. First, the agricultural tradition of many Asian countries, which is rice farming, promotes this skill, and second, Asian languages, Chinese in particular, are better adapted to handling computation of numbers, both leading to an educational climate in which the attributes of a rice-farming tradition and an ease with numbers promote educational and subsequent success in math.
I believe that both are complete sentences.
