Which parts are considered to be customer replaceable units (CRUs) on an HP Compaq dx7500 Business D

Which parts are considered to be customer replaceable units (CRUs) on an HP Compaq dx7500
Business Desktop PC? (Select three.)

A.
optical drive

B.
hood sensor

C.
heat sink

D.
processor

E.
system board

F.
1394 media reader