身份不是固定的；它是流動(dòng)的，不斷演變的。
The world is always ending for someone.
It is India that gave us the ingenious method of expressing all numbers by means of ten symbols, each symbol receiving a value of position as well as an absolute value.
采礦業(yè)的創(chuàng)新不僅僅是技術(shù)，更是思維方式的改變。
I have always preferred working on concrete problems rather than abstract theories.
The best stories are those that haunt us long after we finish reading.