句尾是at once时动词要用什么时态

什么时态,都可以,看下面例句 1。 The man was so genial, so I was drawn to him at once。 这人这么和蔼, 我立刻为他着迷。 dict。cn 2。 We agreed to leave at once。 我们同意立即离开。 dict。cn 3。 Since she is seriously ill, we have to send for a doctor at once。 既然她病得厉害, 我们要马上去请医生。 dict。cn 4。 We determined to go to the railway station at once。 我们决定立刻去火车站。