Mr Johnson _______ a child at the start of the 1950s. [ ]
A. is
B. are
C. was
D. were
答案:C
截至2009年9月30日《建国大业》上映12天(实际11天半)已吸引观众750多万人,这个数字用科学记数法表示为( )人.
A.7.5×106
B.75×105
C.0.75×107
D.7.5×105
拉拔中外润滑油突然中断如何处理?