—Do you know Bill well?

—Yes. We _______ friends since primary school.

 [ ]

A. have turned

B. have made

C. became

D. have been

男，50岁。半年前右上后牙龋病做了充填治疗后一直食物嵌塞，近一周来出现持续性自发性钝痛并有牙龈出血，最可能的原因是

A．充填时未垫底

B．备洞时产热过多

C．深龋使用刺激性较强的消毒药物

D．充填时接触点恢复不良

E．备洞时意外穿髓