—Do you have ?—Yes. But I have an old . A. a toy, ones B. a toy, one C. toys, ones

—Do you have ?
—Yes. But I have an old .
A. a toy, ones B. a toy, one C. toys, ones

解析：本题的回答语用an，表示的是单数，故选项不可能是复数，故不选AC，代替上文所出现的同类事物，单数的可用one来代替，故本题选B。

哦，回答的不错