他是逐渐注意到这种呼吸声的，因而他确实不知道它已经存在多久了。

And he had come to notice this breathing so gradually that he had really no idea how long it had been there.

youdao

他是逐渐注意到这种呼吸声的，因而他确实不知道它已经存在多久了。

And he had come to notice this breathing so gradually that he had really no idea how long it had been there.

youdao