원문은
on the 6th of january we reached teneriffe, but were prevented from landing by fears of our bringing the cholera.
입니다.

그리고 연습문제에
on the 6th of january when we reached teneriffe, but were prevented from landing by fears of our bringing the cholera.
이 문장이 맞는 문장인지 틀린 문장인지 고르는 것이었는데,

저는
(it was) 또는 (we were) on the 6th of january when we reached teneriffe, but were prevented from landing by fears of our bringing the cholera.이고 but 앞문장에 주어가 이미 언급 되어있어서 but were prevented 에 we가 생략되어

when 이 들어간 문장의 when이 관계부사로 본다면 틀렸다고 보기에 애매해서 질문드립니다 . 어떤가요??