Question

    A block chain is a data structure that stores time-ordered data in an ever-growing list, like an accounting ledger (分类账簿). The block chain data structure is maintained using a distributed, peer-to-peer network of computers with no central “master”. As with many new concepts, block chain technology generates much optimism and also a huge amount of interest and excitement. Just what is it good for?

In short, block chains may improve any process where people need to access, confirm, send or store information securely. This information could be a person’s identity, a product’s shipment history or digital property like money.

Typical databases, spreadsheets (电子数据表), and ledgers store information about objects, people, and the interactions between them. Much of the world’s information, from credit card transactions to medical and financial records, is stored in these types of systems.

These types of systems have considerable, well-documented weaknesses that arise from their being centralized. A centralized record is hard to understand and is exposed to unauthorized access or distribution. It is also, because it is a ‘master’ copy, exposed to permanent changing or deletion.

Block chains are also used to store information. Crucially, however, they differ in two ways.

First, information is parceled up into blocks and sealed. Bitcoin, for example, which is the most famous practical example of a production block chain, stores all transactions across the network every ten minutes or so in a single, newly formed block. Each block is then added to the previous one to form a chain.

Second, this “chain of blocks” is not stored centrally. Instead, each block is copied and distributed around an entire network of peers - be they individuals, public institutions, or businesses - using distributed ledger technology. (The terms “block chain” and “distributed ledger” are often used interchangeably; for the sake of clarity, block chain technologies tend to employ distributed ledger technology.)

Each time someone adds a new block to the chain, meanwhile it is added to everyone’s copy.

1.What is the biggest strength of a block chain?

A.It promotes people’s enthusiasm about new technology.

B.It strengthens the security of processing information.

C.It enables people to store more data in time order.

D.It stores a large part of world’s information.

2.The typical systems used to store information are weak in that ________.

A.they are difficult to operate B.they can be accessed easily

C.they have a central “master” D.they store considerable documents

3.The passage is developed mainly by ________.

A.making comparisons B.giving examples

C.making a list D.showing the effect and causes

4.What’s the author’s purpose in writing the passage?

A.To analyze the weaknesses of typical systems.

B.To encourage the popularity of the block chain.

C.To introduce the new concept of the block chain.

D.To compare the two different data structures.

Answer

1.B

2.C

3.A

4.C

【解析】

本文是说明文， 介绍一种新的存储系统——区块链的概念、好处，并比较区块链和典型的存储系统的不同之处。区块链的优势在于增强人们信息处理的安全性。

1.细节理解题。第一段最后提出问题Just what is it good for?（好处是什么？），

第二段回答这个问题：block chains may improve any process where people need to access, confirm, send or store information securely （区块链可以改善任何人们需要安全访问、确认、发送或存储信息的过程）。区块链的优势是增强人们信息处理的安全性。故选B项。

2.细节理解题。根据第四段These types of systems have considerable, well-documented weaknesses that arise from their being centralized. A centralized record is hard to understand and is exposed to unauthorized access or distribution. It is also, because it is a ‘master’ copy, exposed to permanent changing or deletion 可知，这种典型的系统有相当大的弱点，而这些弱点产生于它们的集中化。集中记录很难理解，并且暴露在未经授权的访问或分配中。也是因为它是 “主”本，会遭到永久更改或删除。因此这种系统的缺点在于集中化。故选C项。

3.推理判断题。根据第5段Block chains are also used to store information. Crucially, however, they differ in two ways（区块链也被用来存储信息。但关键的是，它们在两个方面有所不同）可知，文章是围绕将区块链和典型的存储系统作比较而展开的。下文是说明区块链存储信息方式的不同。故选A项。

4.推理判断题。文章第一、二段介绍区块链的概念和好处，第三、四段介绍典型系统存储信息，第六、七、八段介绍区块链存储信息的不同之处。因此本文是介绍区块链这一新的概念。故选C项。