如果我们想赶上那趟火车，就必须立刻离开。

We have to leave ___promptly if we want to catch that train.

我们尽可能迅速地回复读者的来信。

We try to answer readers' letters as ___promptly as we can.

她答应保守秘密，却立刻跑去告诉了本！

She promised she'd keep it secret and ___promptly went and told Ben!