属于条件性维生素是()。
A.维生素A
B.维生素B
C.维生素C
D.维生素D
E.维生素E
参考答案:D
关于表面粗糙度下列说法错误的是()。
A.提高零件的表面粗糙度,可以提高间隙配合的稳定性;
B.零件表面越粗糙,越容易被腐蚀;
C.降低表面粗糙度值,可以提高零件的密封性能;
D.零件的表面粗糙度值越小,则零件的质量、性能就越好。
No one appreciated his work during his lifetime, but________it is clear that he was a great artist.
A.in the aftermath
B.by the time
C.in retrospect
D.in this eventuality