A shortage is a sign that somebody is keeping the price artificially lower than it would be if supply and demand were allowed to operate freely.
The ladder of success is best climbed by stepping on the rungs of opportunity.
我们都是自己的监狱，自己的狱卒。
The challenges of climate change demand urgent action from the scientific community.
对称性不仅是自然的一种属性，而且是寻找物理定律的指导原则。
希望是长着羽毛的东西，栖息在灵魂里。