"In observational studies, we often have to rely on assumptions that are not directly testable."

The best way to learn is by doing—get your hands dirty in the lab.

True strength is not in the muscles, but in the heart.

压力很大，但我努力保持专注。

法律是一个规则系统，是义务的主要规则与承认、变更和裁决的次要规则的结合。

In every country, the most important thing is the education of the people.

我们穿的衣服应该反映我们想要生活的世界。