根据句意和汉语注释，写出单词的正确形式。
（1）Our English teacher has offered us some useful ____  (建议). I think it will help us a lot in our English study.
（2）Here are two ____ (音乐会) tickets for you.
（3）Daniel ____ (不愿)  to accept my books ,which made me very sad.
（4）____ (比较) this new TV set with the old one, you will see which is better.

    It's a fine day today. The children are playing with their toys.

    Amy has a new plastic cup. It's red. Mike has a new toy truck. It's purple and green. Sarah has a lollipop. It's orange. John has a new bucket. It's green. Bob has a yellow balloon, it's nice.

    Mike and Bob are sharing their toys with others. How happy they are!

根据短文内容，判断正误。

酒精的化学式为C₂H₅OH．计算：

①酒精的相对分子质量为____；

②酒精中C、H、O三种元素的质量比是____；

③23克酒精中含氧元素的质量是____g．