he is much thiner than his father 改错

问题描述:

he is much thiner than his father 改错

he is much thinner than his father (is)
原形容词字尾有「子母子」现象 (即后三个字母和音标的排列是「子母子」)时,则要重覆字尾,再加er
类似的还有sadder,bigger