重点讲解：
1. be able to do sth.
能做到某事；
eg. You'll be able to read in peace.
你就能安心地读书了。
eg. It would be nice to be able to afford to retire earlier.
无后顾之忧而能提早退休当是件幸事。
2. a variety of
各式各样；多种多样；
eg. The island offers such a wide variety of scenery and wildlife.
这个岛屿拥有丰富多样的景致及种类繁多的野生动植物。
eg. People change their mind for a variety of reasons.
人们会由于种种原因改变主意。
3. track down
追踪到；追查到；搜寻到；
eg. She had spent years trying to track down her parents.
她已经花了好多年时间试图追寻父母的下落。
eg. I don't know where that old story came from, I've never been able to track it down.
我不知道这则旧传闻的出处，我从来没能考证出结果。