visit|visits|visited|visiting

我下周需要去看牙医。

I need to pay a ___visit to the dentist next week.

她每周看望父母一次。

She ___visits her parents once a week.

我们这周末正在参观科学博物馆。

We are ___visiting the science museum this weekend.

去年夏天我们看望了祖父母。

We ___visited our grandparents last summer.