.The development of industry has been________gradual process throughout________human existence,from stone tools to modern technology. (2012·浙江,2)
— Excuse me.Is this the right way to the Summer Palace? — Sorry, I am not sure.But it______be.
— Do you want tea or coffee? — ______.I really don’t mind.
Finally they arrived at a place _____ sold cigarettes and some other bargains.
Don’t be worried about his safety.______, he is an eighteen-year-old young man.
More bison were killed.The bison population is thought ______ from 60 million to just a few hundred between 1850 and 1910.