under: 短语和例子under the law 根据法律。 under age 未成年。 under sb.'s hand and seal 经某人签名盖章。 under arms 武装着，手执武器。 under avow 发过誓，在誓言下。 under favour 如果允许(这样说)的话〔多作插入句〕。 under fire 在弹雨下，冒着炮火 (land under fire
Example Sentences:
1.
If an arm is stretched forward under water resistance is increased and a reaction force backward is developed , both of which would contribute to negative acceleration 如果手臂在水中是向前伸展则阻力会随之增加而向后方的反作用力也会出现，二者都会产生负加速度。
