A、They shared many extracurricular activities. B、They had known each other since childhood. C、They shared mutual friends in scho

　　(16)I first met Joe Ganz when we were both nine years old, which is probably the only reason he’s one of my best friends. If I had first met Joe as a freshman in high school, we wouldn’t even have had the chance to get to know each other. Joe is a day student, but I am a boarding student. We haven’t been in the same classes, sports or extracurricular activities. (17)Nonetheless, I spend nearly every weekend at his house and we talk on the phone every night. This is not to say that we would not have been compatible if we had first met in our freshman year. Rather, we would not $10 ’&have been likely to spend enough time getting to know each other due to the lack of immediately visible mutual interests. In fact, to be honest, I struggle even now to think of things we have in common, but maybe that’s what makes us enjoy each other’s company so much. (18) When I look at my friendship with Joe, I wonder how many people I’ve known whom I never disliked, but simply didn’t take the time to get to know. Thanks to Joe, I have realized how little basis there is for the social divisions that exist in every community. Since this realization, I have begun to make an even more determined effort to find friends in unexpected people and places.
　　16.  Why does the speaker say Joe Ganz became one of his best friends?
　　17.  Where does the speaker spend most of his weekends?
　　18.  What has the speaker learned from his friendship with Joe?