---Are you a teacher?-No but I .A. used toB. used to beingC. used to beD. was used to

问题补充：

---Are you a teacher? ---No, but I .

A. used to

B. used to being

C. used to be

D. was used to

答案：

A. used to

B. used to being

(答案→)C. used to be

D. was used to

解析：考查不定式的省略：意思是“—你是老师吗？—不是，但我曾经是老师。” used to be 是“过去曾经是”的意思，be used to 是“习惯于……；被用于……”的意思。作固定搭配，不可省略be. 问句有助动词或be动词时 回答要与前面保持一致 若有动词则省略used to 后面的动词以避免重复，如果是be动词则不可省略be动词。选C。