根据汉语意思完成英文句子。 1. 微波炉可以用来煮饭。 A microwave oven can _____  _____  _____ cooking. 2. 你必须亲自去签收，他们不能邮寄过来就算。 You have to go sign for it _____  _____, they can't just mail it. 3. 人类怎么会说这么多种语言，这种情况是如何产生的呢？ How did it _____  _____ that humans speak so many different languages? 4. 老师告诉我们噪音对我们的耳朵伤害很大。 The teacher told us that noise _____ very _____  _____ our ears. 5. 在每一项发明被发明出来之前，爱迪生总要做大量的实验。 Before each invention was invented, Thomas Edison always did _____  _____  _____  _____.