甲、乙、丙三人进行射击测试，每人10次射击的平均成绩恰好都是9.4环，方差分别是S²=0.90，S_乙²=1.22，S_丙²=0.43，在本次射击测试中，成绩最稳定的是       .

According to behaviourist psychology, learning a language is a process of acquiring a set of appropriate ______ chains, a mechanical process of habit formation.

A. stimulus-response


B. question-answer
C. requirement-offering


D. negative-positive