1.This week's class was duller than last (week's).
这周的课比上周的更加枯燥无味。
2.By 1-2 years: teeth are duller and the back teeth may have some yellowing.
2岁，牙齿钝化，后槽牙或许还有点发黄。
3.The British economy is not alone in expecting a duller future.
英国不是唯一被认为是有着暗淡未来的国家。
4.It is true that some books are duller than other.
的确，有些书要比其他书枯燥些。
5.It is true that some books are duller than others.
的确，有些书要比其他书枯燥一些。
6.This week's class was duller than last.
这周的课比上周的更加枯燥无味。