have has down since 过去式是什么意思？

Question

如题所述

Answer 1

这个形式是说:
since表示“自从……以来”，主句用现在完成时，即have戓has+动词的过去分词。从句用一般过去时。
例如:
She has learned English for six
years since she came to middle
school.自从上中学，她已经学了6年英语了。