Answer
Both ligand binding and allosteric regulation involve a molecule (ligand or allosteric regulator) binding at one site and, thus, changing the shape of a protein (receptor or enzyme) at other sites on the same structure. That, in turn, leads to altered activity (signalling or enzyme action) elsewhere in the protein.
Work Step by Step
This question is asking you to see a general property of proteins with their complex structures: that binding at one site alters shape and, thus, other activities if the protein.
