用所给单词的适当形式填空.

1. We are ______ (surprise) at what he does.

2. Tom, someone _______ (wait) for you in your office.

3. — Where _______ David ______ (swim)?

   — I can't find him.

4. We have fun _______ (talk) .

5. The zoo is a good place _______ (have) fun.

小侯同学在学习了燃烧与燃料的有关知识后，观察到家庭用的燃煤通常加工成蜂窝状，这样会燃烧得更充分。由此她联想到细铁丝在空气中不能燃烧，而在氧气中能剧烈燃烧。于是引发了思考：哪些因素能影响可燃物燃烧的剧烈程度呢？她作出两种猜想并进行了实验探究。请你回答有关问题：    

(1)她提出的两种猜想是：    

①____                                                               ；    

②____                                                               。    

(2)请选择其中的一种猜想，设计实验加以探究（你所选择的猜想序号是____）：

(3)为了使燃料能够得到充分利用，节约能源，请你结合燃料使用的实际，提出一条具体建议：                                                                     。