1.mr tuan has just given the children some gifts
-->the children...........................
2.she often spends 20 minutes reviewing her lesson before class
-->it took................................
3.my parents have given me an interesting book
-->I...................................
4.nam is more intelligent than his brother
-->nam's brother is not ...................
5.they are going to build a new supermarket in this town next year
-->a new supermarket.............
6.i can't show you the way to the nearest station because i don't have a map
-->if....................
7.mary took some photographs last year,and they are being shown in an exhibition
-->some photographs.....................