阅读理解
Last year my summer holiday was spoiled by my bringing along a modern convenience that was too convenient for my own good: the iPad. Instead of looking at nature, I checked my e-mail. Instead of paddling a small boat, I followed my Twitter feed（推特简讯）. Instead of reading great novels, I stuck to reading four newspapers each morning. I was behaving as if I were still in the office. My body was on vacation, but my head wasn't.
So this year I made up my mind to try something different: withdrawal from the Internet. I knew it wouldn't be easy, since I'm bad at self-control. But I was determined. I started by giving the iPad to my wife.
The cellphone signal at our house was worse than in the past, making my at tempts at cheating an experience in frustration （沮丧）. I was trapped, forced to go through with my plan. Largely breaking away from e-mail, Twitter and my favorite newspaper websites, I had few ways to connect to the world except for the radio—and how much radio can one listen to, really? I had to do what Ihad planned to do all along: read books.
This experience has had a happy ending. With determination and the strong support of my wife, I won in my vacation struggle against the Internet, realizing finally that it was I, not the iPad, that was the problem. I knew I had won when we passed a Star bucks and my wife asked if I wanted to stop to use the Wi-Fi.“I don't need it,” I said．
However, as we return to post-vacation life, a harder test begins: Can I continue when I'mback at work?
There are times when the need to know what's being said right now is great. I have no intention of giving up my convenience completely. But I hope to resist the temptation to check my e-mail every five minutes, which leads to checking my Twitter feed and a website or two.
I think a vacation is supposed to help you rest your brain to become more productive. Here I hope this one worked.
的中点，点P是直径MN上一动点，若⊙O的半径为1，则AP＋BP的最小值是