根据材料，完成题。
What Should Be Taught
If it were only necessary to decide whether to teach elementary science to everyone on a mass basis or to find the gifted few and take them as far as they can go, our task would be fairly simple. The public school
system, however, has no such choice,51the jobs must be carried on at the same time. Because we depend so52upon science and technology for our progress, we must produce specialists in many fields. 53we live in a54nation, whose citizens make the policies for the nation, large numbers of us must be educated to understand, to uphold, and when necessary, to judge the work of55. The public school must educate both producers and56of scientific services.
In education, there should be a good balance57the branches of knowledge that contribute to effective thinking and58 judgment. Such balance is defeated by59much emphasis on any one field. This60 of balance involves not only the61of the natural sciences, the social sciences and the arts but also relative emphasis among the natural sciences themselves.62, we must have a balance between current and63 knowledge. The attention of the public is continually drawn to new64in scientific fields and the discovery of new knowledge; these should not be allowed to turn our attention away from the sound, established materials that form. the basis of65for beginners.
请在第__（51）__处填上正确答案。 查看材料

A. whereas
B. though
C. while
D. for