重点讲解：
1. bump into
偶然遇见；意外碰到；
eg. I often bump into him at the supermarket.
我经常在超市碰见他。
eg. They decided to pick a time to bump into each other on purpose.
他们决定选个时间有意邂逅。
2. on the tip of one's tongue
话到嘴边（却没说出来）；
eg. It was on the tip of Mahoney's tongue to say the boss was out.
马奥尼想说老板出去了，话到嘴边却没说出口。
eg. A sarcastic remark was on the tip of her tongue.
挖苦的话到了她嘴边却没说出来。
3. stick out
伸出；探出；
eg. She made a face and stuck out her tongue at him...
她做了个鬼脸，向他吐了吐舌头。
eg. He stuck his hand out and he said, 'Good evening.'
他伸出手说：“晚上好。”
4. be invited to do sth.
（正式）邀请，请求，要求；
eg. Volunteer testers are invited to submit feedback via the web.
他们邀请志愿测试者们在网络上提交反馈信息。
eg. A couple of years ago, he was invited to an important reception.
几年前，他受邀参加一个非常重要的招待会。
