sometimes ,if I was left alone at his desk ( )he worked in the lab, an assistant or a student might come in and tell me perhaps I shouldn't be playing with his office things.
空里可填while 和the moment 答案是while.
能不能帮我分析一下这个句子的成分,前面的那个if...是什么东西,然后如果填the moment 在语法上对不对?