NLTK显示语法错误的标签，什么是正确的POS标签？

Question

什么是POS标签：

The poor can can can the tomatoes.

NLTK显示语法错误的标签：

[('The', 'DT'), ('poor', 'JJ'), ('can', 'MD'), ('can', 'MD'), ('can', 'MD'), ('the', 'DT'), ('tomatoes', 'NNS'), ('.', '.')]