Answer: D

Reasoning:  Dunlop’s β-hypothesis states that the “abnormal” forward placement of the tongue seen in a tongue-thrust swallow is usually an adaptive response to the anterior open bite rather than the primary cause of the malocclusion; therefore it is specifically invoked when planning the management of tongue-thrusting habits [Hanson, 1976, PMID 1271779; Dworkin & Culatta, 1980, PMID 7442160].