Bob usually plays football ____ their spare time.[ ]

A. at          

B. on          

C. about          

D. in

熟地的作用是长于

A．清热凉血，养阴生津

B．清热解毒，凉血止血

C．滋阴补血，益精填髓

D．凉血止血

E．补血止血