I am a beginner for English grammar.
I read following paragraph in my grammar book.
I got your long email about two weeks ago and have been trying to find time to write you back ever since. I have been vary busy lately. In the past two weeks, I have had four tests, and I have another one next week. In addition, a friend has been staying with me since last Thursday. She wanted to see the city, so we have been spending a lot of time visiting some of the interesting places here. We(be) _________ to the zoo, the art museum, and the botanical gardens.
I answered 'were', but right answer from answer key was 'have been'.
Why is the answer "have been", not "were"?
Dose anybody help me?