[求助] 關於時態

tarata

請問一下, 我想表達 "我來到這裡之後就一直忙到現在"

a) after I came here, I have been busy upto now

b) after I come here, I have been busy upto now

請問哪一句正確

我看文法書說子句和主句的時態要相同, 可是來到這的動作是先發生而已經完成, 那這樣是不是應該用 came 呢 ?

謝謝