In this task, you're given an article and an answer. Your task is to generate the fill-in-the-blank question for this answer based on the given article. The blanks are always at the end of the question, and can be filled with more than one word or phrase.

Article: Do you want to have a friend whom you could tell everything to, like your deepest feelings and thoughts? Or are you afraid that your friend would laugh at you, or just can't understand what you are going through? Anne Frank chose the first kind. She lived in Amsterdam during World War II. Her family was Jewish so they had to hide, or they would be caught by the German soldiers. She and her family hid away for two years before they were discovered. During this time the only true friend was her diary, which she called Kitty. In a diary dated on Thursday 15 June, 1944, she wrote, "Dear Kitty, I wonder if it's because I haven't been able to be outdoors for so long that I've grown so mad about everything to do with nature. I can well remember that there was a time when a blue sky, the song of the birds, moonlight and flowers could never have kept me puzzled. That's changed since I was here for a year and a half."
Answer: can understand you
In Anne's opinion, the best friend is one who _ .