Traditionally, college students hold a graduation ceremony to encourage themselves before they ____on their life journey.

A．give up

B．settle down

C．get through

D．set off

患者男，69岁，全口仅余左下7，其余为活动义齿。诉2周前不慎咬硬物，崩掉牙冠一小块，因疼痛不明显未给予重视，近来出现左侧舌根痛，口腔检查见左侧舌根有一溃疡，较恰当的处理是（）

A.拔除左下7

B.切除舌左缘的溃疡

C.放疗

D.调磨左下7锐利边缘，继续观察、随诊

E.泼尼松加利多卡因于溃疡基底浸润注射10次