短缺乃是一种符号，它意味着价格被人为地保持在低于供求双方可以自由行事时的水平。
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.
译文：借鉴前代兴衰，考察当下得失。《通鉴》的写作宗旨，直指现实关怀。
Singing is not just about hitting the right notes; it's about telling a story with your heart.
真空不仅仅是空的空间，而是一个具有自身物理特性的复杂实体。