21) It is conflict and not unquestioning agreement that keeps freedom alive.
22) It was in times of crisis that I finally found out what he was really like.
23) It took the human race millions of years to attain that record.
24) It took a mere twenty-year flick(一瞬) of time to double the limit again.
25) It takes (took) sb. some time to do sth.
26) If it takes less time to bring a new idea to the marketplace, it also takes less time for it to sweep through the society.
27) It will take the council a few weeks to judge the situation before it takes any further action.
28) It is well known that many of our problems are caused at least in part by failure to communicate.
29) It is fairly well known that wild animals survive form year to year by eating as much as they can during times of plenty.
30) It is probably less well known that even with their stored fat, wild animals spend less energy to live in winter than in summer.
