The answer should be had known..This sentence refers something that happened in the past and somebody feel regretted about something backward that they couldn't expect!!
若非假設語氣而是事實如何寫此句,I had known earlier that you wanted to join us, I put your name on the list.前句發生在前,為了區分所以用过去完成式,這觀念有了之後,改成未發生的事件,就用本題句法。再伸 I would have put your name on the list.翻譯為我那時就會將你名字列入清單內,意思是並未列入。此句類型可單独使用,如 I would have d•one it.我那時就該做,而後悔未做。總之,學英文要融會貫通 ,舉一返三,這樣不易忘且很有興趣。
This is one type of conditional clause and tense involoved:-
eg:-
If Clause----------(2)had known ,state of being similar "it was known"&"were made known"==>m.c.
Main Clause-----(2)would have been---Re:-would have put(put, put, put ),
It refers a state of being similar to it was known and were made known.that implies idiomatic ,and the standard usage as in(2).;eg:-
If I had known earlier that you wanted to join us, I would have put your name on the list.---(2) had known.correct is a correct answer,correct in every particular aspect.