"Where is Jack?" in Engpsh.
The phrase comes from the common name "Jack," which is a noun used to refer to a man or boy. "Where" is a pronoun used to ask about the location of a person or thing.
Examples:
Where is Jack? He's at the office.
Can you tell me where Jack is? I need to talk to him.
Jack's not answering his phone. Do you know where he is?
中文翻译：
Jack 在哪里？他在办公室。
你能告诉我 Jack 在哪里吗？我需要和他谈谈。
Jack 没有回电话。你知道他在哪里吗？