sheep可数还是不可数用is还是are

　　The path was no better than a sheep track.

　　那条小路简直就像是羊肠小道。

　　Stefano used a motorcycle to herd the sheep.

　　斯蒂芬诺骑一辆摩托车驱赶羊群。

　　Competitors have six minutes to shear four sheep.

　　参赛者们有6分钟的时间来给4只羊剪毛。