HSK 7-9
Liúgǎn bìngdú zhǔyào qīnxí hūxīdào.
The influenza virus primarily attacks the respiratory tract.
HSK 7-9
Yānwù duì hūxīdào yǒu hěn dà shānghài.
Smoke causes great harm to the respiratory tract.
HSK 7-9
Yīshēng shuō tā yǒu hūxīdào gǎnrǎn.
The doctor said he has a respiratory tract infection.