题目

___ you know how the machine works,you will not have trouble operating it.在空格中填入适当的连接词
答案是once
请帮我分析一下

提问时间：2021-03-29

答案

once
conj.一旦…就…
Once you begin, you must continue.
一旦开了头, 你就应当继续下去.