—_____ English classes do you have every week?

—Five.[ ]

A. How often

B. How long

C. How much

D. How many

氧化反应器中邻二甲苯的进料量为5.6m³/h，密度为0.8793g/cm³，纯度为95%，邻二甲苯的转化率为78%，则反应器出口每小时生成苯酐3742.3kg。