"What are they doing?" is a general question in Engpsh that is used to ask about the current actions of a person or group of people. The structure of the sentence is simple and straightforward, making it an easy question to use in a variety of contexts.

Here are some example sentences in Engpsh with their Chinese translations:

What are they doing? 他们正在做什么？
Can you tell me what they are doing? 你能告诉我他们正在做什么吗？
I wonder what they are doing right now. 我想知道他们现在正在做什么。

This simple Engpsh structure is widely used in daily conversation and can be used in a variety of situations. Whether you're asking a friend, a colleague, or a stranger, this question can help you gain a better understanding of the situation at hand.