1.This picture is ____ beautiful than that one.
答案：less.
fewer只能修饰可数名词复数,表数量上的更少；
less不但可以修饰不可数名词,表数量上的更少；
less还可以放在不能加"-er"的比较级前,意思为“更不...”,与more同样表示比较级,但是意思刚好相反.
2.Rose took good care of her books.
=Rose （looked after) her books (well).
3.Our teacher has got a very good (knowledge) of computer.
固定短语：have a good knowledge of...熟悉/精通...
4.This is 3 yuan.That is 7 yuan.
=That is （more expensive）than this.
两空当然填入more expensive.
4 dearer没法理解,除非是4 yuan dearer还差不多.