A.hAB>0;說明A點(diǎn)高程低于B點(diǎn)B.hAB>0;說明A點(diǎn)高程高于B點(diǎn)C.hAB<0;說明A點(diǎn)高程高于B點(diǎn)D.hAB<0;說明A點(diǎn)高程低于B點(diǎn)