颌下间隙感染处理方法中，下列哪项是错误的

A．全身应用抗生素

B．早期切开引流

C．等待波动出现时切开引流

D．影响呼吸时，应早期行气管切开术

E．切开引流时需切开下颌舌骨肌

We often go to school ________ seven ________ the morning. [ ]

A. at; on

B. on ; at

C. at; in

D. in; at