题目内容：

    The race to 5G is on. All four major US carriers now have some form of 5G wireless, although it’s all limited roll-outs in only a few cities, mostly using expensive phones that won’t support future nationwide 5G networks. We’re tracking the roll-outs monthly on our Race to 5G page.

The early 5G roll-outs are more like a public test than a final product. AT＆T, Verizon, and T-Mobile are all using technologies that only travel about 800 feet from a cell site, which means there isn’t much coverage. All four carriers are waiting for upgrades（升级）to their base stations that will improve coverage, speed, and reliability. Around the end of this year or the beginning of 2020, AT＆T, Verizon, and T-Mobile all intend to launch 5G networks that use the existing 4G spectrum（频谱）, which will have slower speeds but broader coverage.

We’ve tested AT＆T in Dallas and Las Vegas Sprint in Dallas and New York; Verizon in Chicago, New York, and Providence; and T-Mobile in New York. Every month, we’ve been seeing better performance and more new devices. It’s messy. It’s very early days. And if you like new technology, it’s very exciting.

In previous mobile transformations, we’ve seen most of the big changes happening years after the first announcement. Take 4G, for instance. The first 4G phones in the US appeared in 2010. But the sorts of 4G applications that changed our world didn’t appear until later. So following that plan. While we’re getting a little bit of 5G right now, you should expect the big 5G applications to crop up around 2021 or 2022.

5G stands for fifth-generation-cellular（蜂窝状的）wireless, and the initial standards of it were set at the end of 2017. But a set of standards doesn’t mean that all 5G will work the same-or that we even know what applications 5G will enable. There will be slow but responsive 5G, and fast 5G with limited coverage.

1.What is the present state of 5G in the US？

A.Initial exploration. B.Great improvement.

C.Wide application. D.Extensive promotion.

2.Why does the author take 4G for example？

A.To persuade carriers to give up 5G.

B.To remind people of 4G’s importance.

C.To prove 5G takes time to make a greater difference.

D.To show 5G has failed to meet expectations.

3.What’s the author’s attitude to 5G？

A.Cautious. B.Skeptical.

C.Opposed. D.Objective.

4.What’s the best title for the text？

A.Race to 5G B.5G is coming

C.How fast is 5G？ D.What is 5G？