二、精選真題長難句演練
通過以下真題長句的演練分析，希望同學們熟知分析長難句的切入點，將長難句化繁為簡地進行理解。
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]本句主幹是Research has found that…, that引導的是賓語從句，直到句末。此賓語從句是由but連接的兩個表示對比關係的並列分句組成，第一個分句的主幹是IQ predicted leadership skills, 其後是條件狀語從句when the tests were given under low-stress conditions; 第二個分句的主幹是IQ was negatively correlated with leadership, 之前的介詞結構under high-stress conditions作狀語，是個省略結構，補充完整後應為when the tests were given under high-stress conditions。由that is(即，就是說)可知，破折號之後的句子是對前面主句的補充說明。
[參考譯文]研究發現如果在壓力小的時候測試，那麼IQ結果就能預測出領導能力，但如果在壓力大的時候測試，IQ結果就會與領導能力相反——也就是說，它的預測是相反的。
2. But science does provide us with the best available guide to the future, and it is critical that our nation and the world base important polices on the best judgments that science can provide concerning the future consequence of present actions.
[解析]本句是由and連接的兩個並列分句組成，其中第一個分句較為簡單，但要注意does的強調用法。第二個分句中it是形式主語，真正的主語是由that引導的主語從句that our nation and the world base important policies on the best judgments, 第二個由that引導的從句that science…of present actions是定語從句，修飾先行詞judgments。
[參考譯文]但是科學確實為我們提供了對未來的最可靠的指引。關鍵是我們的國家乃至全世界在做出重要決策時，應以科學能提供給我們的、關於人類現在行為對未來影響的最佳判斷為依據。