1. Leonard: Sheldon, just let it go. Sheldon，别纠结了，让它过去吧！
Sheldon：if I could, I would, but I can’t, so I shan’t. 如果我可以的话，我会的，但是我不可以，所以我不会。
例：I will arrive on time if you invite me to the party tomorrow.
What is to become lf me if you go away?
例：I wonder if you agree with my opinion.
例：if I were you, I would not talk to him now.
If there were not for the water vapor in the air, there would be no dew.
主句：should（would或could）+动词原形 从句：过去完成时had +动词过去分词
例：if you had studied harder at that time, you would have entered a better university.
If the second world war had not happened, the economics of USA had not been so advanced.
例：if you were to make up your mind, everything would not be difficult.
拓展1：if only与only if
If only：要是，如if only i were you ；而only if：只有……才，如only if you work hard, can you get promoted.(主句倒装)
拓展2: shan’t, shall not的缩写；Shall 用于第一人称表示征求意见。
2．Sheldon：But……since that’s what it looks like, we can rule that out. 但是，因为“不是看起来的那样”，我们可以排除那种情况。
例：The Treasury Department has ruled out using a weak dollar as the main solution for the country's trade problems.
The disaster ruled her out a permanent future for the ballerina in dancing.
Rule it out：排除可能性
例：The police man thought the most possibility of homicide, but Joe held the view that the woman died from the commit suicide and didn’t rule it out.
3. Sheldon: Although what I lack in leadership, apparently I more than make up for in sewing. 虽然我没什么领导能力，不过我的锋刃技术还不错。
make up for：弥补，补偿
例：I just want to make up for my faults before.
What she lacks in ability makes up for in circumspection.