前提是

“我叫阿曼达·基拉斯多特，”我宣布，“我是来救你们的——前提是你们需要人救。”

“My name is Amanda Kirasdottir,” I announced. “I’m here to save you—assuming you need saving.”

前提是你和吉姆有把床用来睡觉，而不是干别的。

That is, assuming you and Jim use the bed for sleeping, not for anything else.

当然，前提是我活得够久，能用上这招。

Sure, assuming I live long enough to use this trick.