Therespiratory diverticulum initially is inpen communication with the primitiveforegut.Which of the following embryonic structures is responsible for separating these twostructures?()

A．Laryngotracheal groove
B．Posterior esophageal folds
C．Laryngotracheal diverticulum
D．Tracheoesophageal septum
E．Bronchopulmonary segment