When did you first know this bamboo forest
Question: When did you first know this bamboo forest?
⇒How long ________________________________________?
Question: When did you first know this bamboo forest?
⇒How long ________________________________________?
Đáp án: How long have you known this bamboo forest?
Giải thích: When + did + S + Vqk? = How long + have/has + S + Vp2?
Dịch: Bạn biết cây rừng tre này được bao lâu rồi?