Question

【题目】The students should collect waste. It can be used again. （合并为一句）
The students should collect waste be used again.

Answer 1

【答案】that/ which；can
【解析】句意：学生们应该收集那些废品。它可以被再次使用。原句it can be used again中的it代替前句中的waste，句子用来修改waste，可用which或that替换，作定语从句，将which/that引导的整个句子放到waste后面，所以答案是that/ which；can。