【问】 This is the first time I heard her sing.

这是我第一次听她唱歌。

这个句子是否正确?

【答】 在正式英语里，这个句子是错误的。This is the first(second，third... )time这个结构要求后面使用现在完成时，This was the first(second，third... )time这个结构要求后面使用过去完成时。例如：

1. This is the fourth time she’s rung you in a week. (Gronin)

这是她一周内第四次给你打电话。

2. It was the second time he had been out with her alone. (London)

这是第二次他单独跟她外出。

3. That was the first time I had left England’s shores. (Pollitt)

这是我第一次离开英国海岸。

此外，还可以采用It was the first time of somebody’s doing sth.的结构：

It was the first time... of her ever hearing him refer to the period of his suffering.(Dickens)

这是她第一次听到他谈论他受苦的时期。