sheep和rubbish是 可数还是不可数名词

问题描述:

sheep和rubbish是 可数还是不可数名词
如果sheep是可数名词为什么There is (a little)[而不用a few] sheep eating grass at the food of the hill

从哪里看到的?
sheep应该是可数名词,单复数同形.
rubbish不可数.