[译]牛、羊等食草为生。
[误] Cattle, sheep, etc. feed on grasses.

[正] Cattle, sheep, etc. feed on grass.
[注] grass属于集合名词,不用复数形式。又如:The grass grows quickly in the garden.花园里草长得很快。/The grass began to take root and sprout.草开始生根发芽。