0 one of several types of simple chemical substance that are necessary for healthy growth and development, and exist in animals and plants in very small amounts -- 微量元素
We can complete it step by step however long the road is and it can't be completed however short the road is if you don't even mark your footprint.
再长的路,一步步也能走完,再短的路,不迈开双脚也无法到达。