—You were not listening；what troubled you?

—I         my coming math exam．

A．am thinking about

B．was thinking about

C．had thought about

D．will think about

在注采方式不变的情况下区块平均地层压力年升降幅度不超过（）MPa，要严格防止出现油层压力猛升猛降的现象。凡总压差低于（）MPa的都要逐步调整到原始地层压力附近。