单选题 阅读下列文章,选出以下3道题的最佳选项.Today people can use the phone to talk with others almost anywhere on the earth. But when you use the phone, you don't see the person you are talking with. That may change in the near future.Today some people are using a kind of telephone called the picture phone or vision phone. With it, two people who are talking can see each other.Picture phones can be useful when you have something to show the person you' re calling. They may have other uses in the future. One day you may be able to ring up a library and ask to find a book. Then you'll be able to read the book right over your picture phone. Or you may be able to go shopping through your picture phone. If you see something in the newspaper that you think you want to buy, you'll go to your phone and call the shop. People at the shop will show you the thing you're interested in right over the phone. You'll be able to shop all over the town and never leave your room!(3) Picture phones are very _______