计算(﹣2xy3z2)4=( );62×3﹣2×19990=( ).
16x4y12z8,4
She was so________in her job that she didn’t hear someone knocking at the door.
A.absorbed
B.attracted
C.drawn
D.concentrated
当减压转油线出现大泄漏时应采取()措施。
A.减压炉迅速切断进料,单歼常压
B.减压塔破真空
C.减压塔内通人蒸汽,逐步恢复正压
D.降低塔内温度