单项选择题

A.CRHAB≈CRHA×CRHB
B.CRHAB≈CRHA+CRHB
C.CRHAB≈CRHA-CRHB
D.CRHAB≈CRHA/CRHB
E.CRHAB≈(CRHA×CRHB)/CRHA+CRHB