0 any of various types of very small animals with one cell -- 原生动物；单细胞生物
Amoebas are protozoans. 阿米巴虫是原生动物。
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。
