1）It is the first / second time…. that…结构中的从句部分，用现在完成时。
    It is the first time that I have visited the city.
    It was the third time that the boy had been late.
    
    2）This is the… that…结构，that 从句要用现在完成时.
    This is the best film that I've (ever) seen.
    这是我看过的最好的电影。
    This is the first time (that) I've heard him sing.  这是我第一次听他唱歌。
    
    典型例题
    (1) ---Do you know our town at all?  
    ---No, this is the first time I ___ here.
    A. was   B. have been   C. came   D. am coming
    答案B. This is the first time 后面所加从句应为现在完成时，故选B。
    
    (2) ---Have you ____ been to our town before?
    ---No, it's the first time I ___ here.
    A. even, come   B. even, have come    C. ever, come   D. ever, have come
    答案D. ever意为曾经或无论何时，反意词为never，此两词常用于完成时。 This is the largest fish I have ever seen. It is / was the first time that-clause 的句型中，从句要用完成时。
    注意：非延续性动词的否定形式可以与表示延续时间的状语连用。即动作不发生的状态是可以持续的。
    （错）I have received his letter for a month.
    （对）I haven't received his letter for almost a month.