高中的英语句子分析～For such practices, once taken up, are likely to b

问题描述：

高中的英语句子分析～
For such practices, once taken up, are likely to become deeply rooted, to spread, and corrode one'mind.
我想知道once taken up和 to spread在这里做什么成分?
像这种成分内的动词一定要是分词或to+动词吗?

1个回答分类：英语 2014-10-19