19.area 地区,范围;面积;学科的领域; zone 用于地理名词:time zone, the torrid zone 当表``地带,地区’’时,二者可换用. 1)This area/zone will become flooded. 2)What’s the area of China? 3)In the area of language teaching. 4) A danger zone/area.

20.finish/enjoy/practise/mind/suggest/advise+v-ing

21.Please read the reference book(中学教材全解)