他年轻吗英语回答怎么说

To answer whether someone is young or not in Engpsh, you can use the following phrases:

"Is he young?"
"Is she a young person?"
"How old is he?"
"How old is she?"

You can then provide an answer by saying:

"Yes, he is young."
"No, he is not young."
"He is [age] years old."

For example:

Person A: "Is he young?"
Person B: "No, he is not young. He is 35 years old."