Mr Wang was reading in his office alone. Suddenly he heard someone ______ "Help! Help!" [ ]

A. shout

B. to shout

C. shouted

D. shouting

权利要求1为一种精馏方法，权利要求2为权1的从属，其特征在于其中所述的精馏设备由A、B和C三个部分顺序连接而成。权利要求2由于采用设备特征限定精馏方法，因此不清楚。