0 an actor who learns the parts of other actors in a play, so that he or she can replace them if necessary, for example if they are ill -- 候補演員,替角
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。