--How many people were there at the meeting?-- . All the people went on a trip to Beijing.

问题补充：

--How many people were there at the meeting?

-- . All the people went on a trip to Beijing.

A. Nobody

B. No one

C. None

D. Nothing

答案：

A. Nobody

B. No one

(答案→)C. None

D. Nothing

解析：这几个词都表示否定含义，none 既可以指代物也可以指代人，no one ,nobody只可以指代人，nothing只能够指代物；nobody, no one, nothing只能单独使用，后面不跟of短语。； nobody, no one, nothing和none常用作简略答语，一般情况下，nothing回答what问句； nobody和no one回答who问句；none回答how many或how much问句。根据上文，会议上有多少人？根据下文，所有人都去北京旅行了。可知此处指的是一个人也没有。故选C。