Why is the two scientists work so important to science?
In the 1920s,Satyendra Nath Bose was studying an interesting ____about special light particleswe now call photons.Bose had trouble ____ other scientists to believe his theory，so he contacted Albert Einstein.Einsteins calculations helped him theorize that atoms ____behave as Bose thought-but only at very cold temperatures.
Scientists have also discovered that ultra-coldatoms can help them make the worlds atomic clocks even ____accurate.These clocks are so accurate today they would only lose one second ____six million years! Such accuracy will help us travel in space because distance is velocity times time.With the long distances involved in space ____，we need to know time as accurately as possible to get accurate distance.
51.A. operated B. opened C. offered D. occurred
52.A. space B. star C. Earth D. planet
53.A. where B. what C. when D. whether
54.A. sadly B. repeatedly C. Freely D. safely
55.A. energy B. year C. system D. rays
56.A. by B. along C. away D. With
57.A. location B education C status D knowledge
58.A. interesting B. impossible C. reasonable D. necessary
59.A. burnt B. cooled C. blown D. cut
60.A. invention B. experiment C. paper D. theory
61.A. forcing B. begging C. convincing D. ordering
62.A. will B. would C. must D. need
63.A. that B. such C. more D. much
64.A. every B. any C. each D. some
65.A. station B. craft C. age D. travel
答案：DADDC CABBD CBCAD