我们现在靠写信与他保持联系。

We now keep in touch with him by writing letters.

youdao

自从我们分手以来，我一直与他保持联系。

I have kept in touch with him since we separated.

youdao

自从我们分手以来，我一直与他保持联系。

I have kept in touch with him since we parted.

youdao

And he kept track of how many people he gave the vaccines to, and then he kept track of what would happen to those people when a smallpox infection occurred in their community.

他与接种过牛痘的人保持联系,关注当天花在这些人周围肆虐时,他们身上发生了什么

耶鲁公开课 - 生物医学工程探索课程节选