— Did Peter fix the computer himself?

— He __________, because he doesn’t know much about computers.

A．has it fixed

B．had fixed it

C．had it fixed

D．fixed it

鉴别急性牙髓炎上下牙位

A．电诊法
B．X线检查
C．染色法
D．麻醉试法
E．嗅诊 检查下列疾病必须应用的方法是