精选真题长难句演练
通过以下真题长句的演练分析，希望同学们熟知分析长难句的切入点，将长难句化繁为简地进行理解。
1. Research has found that IQ predicted leadership skills when the tests were given under low-stress conditions, but under high-stress conditions, IQ was negatively correlated with leadership—that is, it predicted opposite.
[解析]本句主干是Research has found that…, that引导的是宾语从句，直到句末。此宾语从句是由but连接的两个表示对比关系的并列分句组成，第一个分句的主干是IQ predicted leadership skills, 其后是条件状语从句when the tests were given under low-stress conditions; 第二个分句的主干是IQ was negatively correlated with leadership, 之前的介词结构under high-stress conditions作状语，是个省略结构，补充完整后应为when the tests were given under high-stress conditions。由that is(即，就是说)可知，破折号之后的句子是对前面主句的补充说明。
