1，I have preheated the oven 我已经预热了炉子

2，You can put it in the oven 你能把它放在炉子里

3，all you have to do is washing the patatoes 你所要做的就是洗土豆

4，The water may boil over 这个水有可能沸出来

5，You must supervise 你必须监督好

6，You can cut it up 你能把它切碎

7，You can pour some milk into the bottle 你能倾倒一些牛奶在瓶子里

8，You have to buy some potatoes 你必须买一些土豆