The chances are that you’ve walked past a QR Code(二维码) or come into contact with one recently, possibly without noticing. Even if you haven’t seen one before, here are some examples for you.

But what exactly are QR Codes? Very simply, they are bar-codes, not too dissimilar to the bar-codes you saw on the package of almost every product you bought. QR Codes are combined with multiple rows and columns(列), which allows QR Code to stone its data.
QR Codes started out in the East but their popularity exploded worldwide within a few years. They are flexible, cheap, easy to read by scanners as simple as an App on your smart phone and easy for anybody to create. The direction of reading the QR codes is not limited. Even when damaged there is a chance that they are still readable. Unlike traditional bar-codes which are 1 dimensional (using 1 row of lines), QR Codes use 2 dimensions, which allows them to store a lot more data in the same area of space.
But can a picture or music be stored in a QR Code? Images and sounds consume much more data than text and a QR Code is limited to storing 3kb of data. The size of an image will need to be made so small to be stored that it will be impractical to do so. So it is with songs. In fact if you have a need to present the user with an image or kick off a music stream when they scan your QR Code, why not look to host it somewhere and then have your QR code simply linked to the content?
Not only have QR Codes surely brought us great convenience, but also security concerns at the same time. For example, a QR Code may be covered by one designed by a cheater on purpose, without being recognized. You sign up entering all your account details only to find the following day someone has gained access to your account because of the information you entered in that website.
1.What do we know about QR Codes?
A. They can be scanned from any direction
B. They use 1 row of lines to store data.
C. They are readable when damaged.
D. They are flexible but not cheap.
2.Which is one big drawback of QR Codes?
A. A QR Code can be linked to somewhere else.
B. QR Codes cannot be used to present a picture.
C. A QR Code can store data of no more than 3kb.
D. QR Codes can only be read with an app on your smart phone.
3.From the text we can infer that _______.
A. traditional bar-codes have an advantage over QR codes in storing data
B. we had better pay attention to the security when using QR codes
C. it makes sense to store a song of a picture in a QR code
D. QR Codes are so dangerous that they are not worth using
4.The text mainly talks about______.
A. the use of QR Codes
B. the disadvantages of QR Codes
C. the advantages of QR Codes
D. the formation of QR Codes