单选题
It was not long before Skinners, the famous behaviorist, {{U}}realized{{/U}} the limitations of his psychological research {{U}}than{{/U}} another psychologist came with his forceful arguments against Skinners' theory.
【正确答案】
B
【答案解析】[分析] 结构应用
本句意为：当另一个心理学家提出反对Skinner理论的强有力论据后不久，Skinner这一著名的行为主义心理学家就意识到自己在心理学研究上的局限了。在表示过早发生某事或刚刚……就……的时间状语从句中，常用when来连接；在it was not long before... when...句式中，主句用过去完成时，从句用过去时；所以答案为B。