【答案解析】解析：句意：他一到就会立刻打电话给你。本题考查的是as soon as引导时间状语从句的用法。as soon as一般有两种情况：(1)指未发生的动作，主句用一般将来时，从句用一般现在时代替一般将来时，例：I will tell him the news as soon as he comes back．(2)指紧接着发生的两个短动作，主从句都用一般过去时，例：He took out his English books as soon as he sat down．A为现在进行时，B为一般将来时，故选C。