一道SAT改错
Havingcompletedacourseinartappreciation,MaureenandIwereabletojudgethepaintingsintheMuseumofModernArtmorecriticalthanwehadbefore.
请问后面怎么能用had?
只见过前面是sth或者doing后面用had的
前面是动词的话为什么还是had?