.The development of industry has been________gradual process throughout________human existence,from stone tools to modern technology. (2012·浙江,2)
I still remember ____ to the Summer Palace and what I saw there.
The scientist’s many years’ careful observation ____ a surprising discovery.
Don’t come and see me today – I’d rather you ____ tomorrow.
It is clear that your ____ English will greatly improve if you can practice ____ wherever you can.
This means going back to the place where we left the family ____ in a tree the night before.