重点讲解：
1. at first sigh
乍一看；一见之下；初看时；
eg. It promised to be a more difficult undertaking than might appear at first sight.
那项任务可能比乍看之下还要困难。
eg. At first sight it resembles a traditional village of two-storeyed, balconied houses, set among well-tended gardens.
乍一看，它就像个传统的村庄：带阳台的两层楼房坐落于精心照料的花园中。
2. single out
单独挑出；特别选出；
eg. His immediate superior has singled him out for a special mention...
他的顶头上司特别提到了他。
eg. We wanted to single out the main threat to civilisation.
我们想特别指出威胁文明的主要因素。
3. feed on
用……喂养； 靠吃……过活；
eg. These larvae feed on planktonic algae.
这些幼虫以浮游海藻为食。
eg. In flat open country there is plenty of grass for the cattle to feed on.
在开阔平坦的地区有大量的青草供牛群食用。