省略是避免重复，突出新信息并使上下文紧密连接的一种语法手段。在英语中，为了使句子简洁明快，突出重点，常用“省略句”，
只要不影响句意的表达，能省略的成分尽可能省略。省略的结果，不但句子结构显得紧凑，而且句子中几个关键词如is,will
be,might be 等的意义也被突出出来。省略不仅是句子成分的粘着手段，而且是句子之间的承接纽带。
Some books are to be tasted, others (are) to be swallowed ,and some few(are) to be chewed and digested.
The picture wasn't finished. If it had been (finished), I would have brought it.
