younger
原因如下：参考比较级的语法
比较级前的修饰语
在使用比较级的时候,为使比较的程度更加确切,可以在比较级前加上一些修饰语,这些修饰语有：
1．数词短语,用来表示具体的数量
My sister is two years older than I.
2．a little,a bit表示“一点儿”,稍微之意
She is a little shorter than Han Mei.
This book is a bit thicker than that one.
3．some（肯定句）,any（否定句、疑问句）,表“…一些”
I’m feeling some better.
The man was too tired to go any farther.
4.much,a lot,by far表示“…得多”
Out school is much more beautiful than it was before.
5．Still,even表“…更…”,“…还是…”
My watch is expensive,but this is even more expensive
注：very,quite,more等词一般用来修饰形容词、副词的原级,不能用来修饰比较级.