beef是可數名詞還是不可數名詞

　　The smell of roast beef permeated the air.

　　烤牛肉的氣味彌漫在空氣中。

　　Japan is the biggest importer of U.S. beef.

　　日本是美國牛肉的最大進口國。

　　Thick tuna steaks are eaten rare, like beef.

　　厚厚的金槍魚片要半熟吃，就像牛肉一樣。