https://online2.tingclass.net/lesson/shi0529/0009/9907/624.mp3
https://image.tingclass.net/statics/js/2012
講解文本：
rack one's brain 絞盡腦汁，努力思索
Write them down and then you won't have to rack your brain anymore!
把這些都寫下來，你就不用每次都拼命想了。
The test is too hard. I have been racking my brain for days.
這個測試太難了，我已經(jīng)絞盡腦汁想了幾天了。
