Choose the correct phrase to complete the alien tourist's postcard home.

Earth is exhausting! I ______ three human cities so far this week, and I still haven't found any good pizza.

The correct answer is have visited.

We use the Present Perfect (have visited) for actions that happen in an unfinished time period (like "this week", "today", or "so far"). Because the week isn't over yet, the alien might visit more cities!

If the postcard said "last week" (a finished time), then the Past Simple "visited" would be correct.