iron是可數(shù)名詞嗎

　　A boy came towards them, rolling an iron hoop.

　　一個(gè)男孩滾著一個(gè)鐵環(huán)朝他們走來(lái)。

　　Iron reacts with water and air to produce rust.

　　鐵和水及空氣發(fā)生反應(yīng)產(chǎn)生鐵銹。

　　I'll need to iron that dress before I can wear it.

　　我得先把那件連衣裙?fàn)C平再穿。