1. buoyant

If you are in a buoyant mood, you feel cheerful and behave in a lively way.

e.g. You will feel more buoyant and optimistic about the future than you have for a long time.

2. riv 词根，拉丁，表示“河流，路途，引导”

derive: If you derive something such as pleasure or benefit from a person or from something, you get it from them.

e.g. Mr. Ying is one of those happy people who derive pleasure from helping others.

3. mend 词根，表示free from fault 修补，改进

amend: verb 

if you amend something that has been written such as a law or something that is said, you change it in order to improve it or make it more accurate.

e.g. The amended version of the Act.

4. stifling 

stifling heat is so intense that it makes you feel uncomfortable. You can feel uncomfortable. You can also use stifling to describe a  place that is extremely hot.

e.g. The stifling heat of the little room was beginning to make me nauseous. 

5. orthodox 

Orthodox

ortho 正确的

e.g. Orthodox police methods

6. stifle

If someone stifles something you consider to be a good thing, they prevent it from continuing.

e.g. Critics have accused the US of trying to stifle debate.

7. ominous

If you describe something as ominous, you mean that it worries you because it makes you think that something unpleasant is going to happen.

e.g. There was an ominous silence at the other end of the phone.

8. cru 十字，交叉

crux: the crux of a problem or argument is the most important or difficult part of it which affects everything else.

He said the crux of the matter was economic policy.

9. fall 过错，欺骗

A fallacy is an idea which many people believe to be true, but which is, in fact, false because it is based on incorrect information or reasoning.

It is a fallacy that the affluent give relatively more to charity than less prosperous.