0 a hard substance in the outer shell of insects and animals such as shrimp and lobster, and in the cell walls of some fungi -- 甲殼素(某些生物(如昆蟲、蝦和龍蝦)保護外層中的一種堅韌物質,也存在於某些真菌的細胞壁)
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。