结果一致的Ⅰ级临床研究结论属于（）
A.E级
B.D级
C.C级
D.B级
E.A级
参考答案：E
In those days, books _____ one at a time by hand. [ ]
A. should be produced
B. should be produce
C. could be produced
D. could produce
冲模的装配，最主要的是保证（）和（）的对中，使其间隙均匀
