单项选择题 DDN中若采用X.50建议,数据信号速率为4800bit/s,包封后速率为()A.3200bit/sB.4800bit/sC.6400bii/sD.12800bit/s
未知题型 Young children sometimes cannot distinguish between ________ and reality.A allusionB fantasyC fancyD image
单项选择题 在86.0kPa压力下用水蒸气蒸馏甲苯,已知在此压力下该系统的共沸点为800C, 800C时水的饱和蒸汽压为47.3kPa.欲蒸出100g甲苯,需消耗水蒸气()克. M=92g/mol。 A. 32.7 B. 47.3 C.23.9 D.100