释义：君子在面对挫折、困难的时候，应该反躬自问，修养品德。蹇（jiǎn），多指行动迟缓、困苦、不顺利的意思。
Efficiency in energy production is the cornerstone of sustainable development.
Mathematics is not about numbers, equations, computations, or algorithms: it is about understanding.
Innovation without sustainability is just another form of exploitation.