◎看看发起者是谁，用意思来判断

 Coronary angiography, a sophisticated method for diagnosing coronary disease, involves the introduction of a dye into the arteries of the heart and is now administered selectively, because it uses x-rays to observe cardiac function. (A-P1-137)

 A. method for diagnosing coronary disease  involving the introduction of a dye into the arteries of the heart and is now administered selectively, because it usesinvolving 的发起者为disease主要分析分词及主干的谓语动词

 ◎时间和地点状语不放在动词和发起者之间

 ◎意义无区别时: 2个选项比较：最好用动词形式，不用名词或形容词形式Section 18.13. Oberlin College in Ohio was a renegade institution at its 1833 founding for deciding to accept both men and women as students.

 (A) at its 1833 founding for deciding to accept

 (B) for the decision at its 1833 founding to accept

 (C) when it was founded in 1833 for its decision to accept

 (D) in deciding at its founding in 1833 to accept

 (E) by deciding at its founding in 1833 on the acceptance ofD

 ◎只要没有明显表示时间概念的词或者时间概念就不要考虑时态，但如果有就立刻考虑，只有现在、过去、进行、将来和完成时

 ◎如果划线部分的头尾是V，先做V。

 看动词。如果画线部分有动词开头或者结尾， 先找动词的发起者， 根据事态， 单复数等可以排除选项。时间，地点状语不可插在动词与动词发起者之间， 应放在之前或者之后。动词中的非100%原则：动词原型与动词的衍生名词；主动与被动；一般事态的优先原则。Section 18.15. People have discovered the principles of solar energy whenever fuel becomes scarce and expensive but will forget them every time a new source of cheap energy is developed.

 (A) have discovered the principles of solar energy whenever fuel becomes scarce and expensive but will forget

 (B) have discovered the principles of solar energy whenever fuel has become scarce and expen-sive but they forget

 (C) discovered the principles of solar energy every time fuel becomes scarce and expensive,forgetting

 (D) discover the principles of solar energy every time fuel became scarce and expensive, but they forget

 (E) discover the principles of solar energy whenever fuel becomes scarce and expensive but forget

 whenever, every time 一般现在时, E