We had guests last night who have not stayed in a B&B hotel ago. They did not want breakfast because that they were going out early in the morning. They came back lately and had some tea. I came into the living room and saw one of them just go through the kitchen door but turn on the light. He was looking for a glass the cupboard. He had no ideas that the kitchen was not for guests. I just smiled to me and thought, "What can I do We are guests after all. \

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线路板设计中钻孔层在哪一层（）。

A.23层

B.24层

C.25层