beef是可数名词还是不可数名词

The smell of roast beef permeated the air.

烤牛肉的气味弥漫在空气中。

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

日本是美国牛肉的最大进口国。

Thick tuna steaks are eaten rare, like beef.

厚厚的金枪鱼片要半熟吃，就像牛肉一样。