On the graduation day, he received from his father a nice present       a note was attached, saying “I’m proud of you.”

A．on which

B．to which

C．with which

D．in which

换热设备投用时，（）流量正常后，须再次进行全面检查，以防由于温度和压力的变化引起跑、冒、滴、漏等问题。