The weather is not as cold (as you think). So (I don' t think) the ice is thick (enough) to (walk on it).
【正确答案】 D
【答案解析】重复错误，应把it去掉。此处to walk on是不定式做后置定语，修饰thick，on的宾语是 ice，承前词省略，因此不需要it做宾语。