be present at和be present in都对吗？若都对请分别给出一个例句，并解释其区别
be present at
存在于(出现于)
Viruses may be present in tapwater.
病毒可以存在于自来水中。
Aerosols are present throughout the atmosphere.
气溶胶存在于整个大气层。
be present in
存在于(出现于)
Viruses may be present in tapwater.
病毒可以存在于自来水中。
Aerosols are present throughout the atmosphere.
气溶胶存在于整个大气层。
存在于(出现于)
Viruses may be present in tapwater.
病毒可以存在于自来水中。
Aerosols are present throughout the atmosphere.
气溶胶存在于整个大气层。
be present in
存在于(出现于)
Viruses may be present in tapwater.
病毒可以存在于自来水中。
Aerosols are present throughout the atmosphere.
气溶胶存在于整个大气层。
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第1个回答 2015-01-13
How many people were present at the meeting yesterday.
They is present in the classroom。be present 出席的。到场的，存在的，in at 取决于其后的名词追问
They is present in the classroom。be present 出席的。到场的，存在的，in at 取决于其后的名词追问
第二句应为they are吧
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