19) It is only recently that science has begun to give us some idea of how the brain really works
20) It was not until the century that man realized that the whole of the brain was involved in the working of the mind.
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.
31) It remains unknown whether there are intelligent beings outside the solar system.
32) It has been pointed out that in 6000B. C. the fastest transportation available to man over
33) It is now thought that the more work we give our brains, the more w** able to do.
34) It can be argued that such a response may not mean much (有人认为……)
35) It is reported that the electronic industry is going on rapidly in recent year.
36) It is reported that there has been a decrease in the annual birth rate over the last two decades.
37) It is estimated that the total expenses in the trial manufacture of the new products will come to 30,000 yuan.
38) Once it was thought that nighttime dreams interfered with our needed rest.
39) It has been observed that unemployment brings enormous psychological troubles.
40) Even so, it seemed to him that he was part of the whole event.
41) It seems to me that the Americans are a highly mobile people. Most of them like to travel whenever they get the chance.
42) It seemed to me that the only thing that mattered was to get her husband back to her.
43) But it is only because it is my work to do so.
44) It is an encouraging sign that people s purchasing power(购买力)is on the rise.
45) It is common knowledge that chalk absorbs moisture (湿气) from the air.
46) It might be a way to avoid the indignity of having to ask for money all the time.
47) It used to be a popular belief the we could foretell a person s future on the basis of the date and time of his birth.
48) It pays in the long run (从长远的角度看……) to introduce new technique
49) It is time for out symbols of technology to change — to catch up with the quickening changes in technology itself.
50) It has been only twenty-five years since television came to one of people s pastimes.