Scientists have to work hard to keep ________ with modern discoveries and developments.
. The post-Expo fate of foreign pavilions, especially those _____ tens of millions of dollars, has aroused strong interest among the public.
______abroad for a tour can be a worthwhile experience to a senior high student.
It was a pity that the great writer died with his work _______.
It is the farm to which we are going to pay a visit ______ provides large quantities of green vegetables for the nearby town every year.
If you have never planted anything, you won’t be able to know the pleasure of watching the thing you have planted ____.