The angular displacement equation of a straight bar with constant cross-section represents what relationship of a single span statically indeterminate beam?

A、Therelationshipbetweentheexternalfactors,suchasloadanddisplacement,andthememberendforce；;
B、Therelationshipbetweenloadandmemberenddisplacement;;
C、Therelationshipbetweenloadandmemberendforce;;
D、Therelationshipbetweenmemberendforceandmemberenddisplacement.