Smith has no money to buy a bike, ________ a car.
A. not mention
B. let alone
C. neither is
D. nor does
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Practise ________ every day and you will improve your pronunciation.
A. read
B. to read
C. reading
D. to be reading
Tell me the news ________ you get it.
A. before
B. until
C. once
D. beyond
评定表面粗糙度的取样长度一般默认含有()个评定长度。
A. 5
B. 3
C. 7
D. 9
选择表面粗糙度评定参数数值时,下列论述不正确的有( )
A. 同一零件上工作表面比非工作表面参数值大。
B. 摩擦表面应比非摩擦表面的参数值小。
C. 配合质量要求高,表面粗糙度参数值应小。
D. 受交变载荷的表面,表面粗糙度参数值应小。