Cyril Burt's Study of Separated Identical Twins Was Briefly Considered

Cyril Burt's study of separated identical twins was briefly considered to be the best of its kind primarily because of its claim that

A) its twin pairs had been placed completely randomly in a full range of adoptive families.
B) its twin sample had been collected over a period of several decades.
C) the intelligence tests it employed were more reliable than in other studies.
D) it used the most sophisticated statistical procedures to arrive at its results.