'Unless' in the Bible

"Why, how can I," replied the eunuch, "unless some one explains it to me?" And he earnestly invited Philip to come up and sit with him.

But certain persons who had come down from Judaea tried to convince the brethren, saying, "Unless you are circumcised in accordance with the Mosaic custom, you cannot be saved."

unless it was in that one expression which I made use of when I shouted out as I stood among them, "'The resurrection of the dead is the thing about which I am on my trial before you to-day.'"

But Paul, addressing Julius and the soldiers, said, "Your lives will be sacrificed, unless these men remain on board."