【正确答案】正是这种突然地认识到人类无知的深度和广度，才代表了20世纪科学对人类智能的最大贡献。

【答案解析】[结构分析] 句子框架是It is this sudden confrontation...that represents the most significant contribution...。It is...that...引导强调结构，强调主语。confrontation with原意为“与…迎面相遇或正面相对”，此处转译为“认识到”；contribution...to译成“对…的贡献”。