Which process is responsible for writing the contents of database buffers to data files?

A.
Process Monitor process (PMON)

B.
Listener Registration process (LREG)

C.
System Monitor process (SMON)

D.
Database Writer process (DBW)

E.
Log Writer process (LGWR)

F.
Checkpoint process (CKPT)

Explanation:
http://docs.oracle.com/cd/E11882_01/server.112/e25789/process.htm#CNCPT1254
(see database writer process (DBW))