题目内容：

    China’s war on garbage is as digital as the country itself. Think QR codes attached to trash bags that allow the government to trace exactly where its trash comes from.

On July 1, Shanghai began a compulsory garbage sorting program. Households and companies must classify their wastes into four categories and dump them in appointed places at certain times. The strict program became a headache for some residents. Not even the most environmentally conscious person can get all the answers right. Like, which bin does the newspaper you just used to pick up dog poop (粪便)belong to?

Gratefully, China’s tech startups are here to help. For instance, China’s biggest internet companies responded with new search features that help people identify what wastes are “wet”, “dry”, “toxic”, or “recyclable”. Simply pull up a mini app on WeChat, Baidu or Alipay and enter the keyword. The tech firms will give you the answer and why.

Alipay, Alibaba’s electronics payment company, claims its garbage sorting mini app added one million users under just three days. The mini app has so far indexed (编索引) more than 4,000 types of rubbish. Its database is still growing, and soon it will save people from typing by using image recognition to classify trash when they snap a photo of it. If people are too busy or lazy to hit the collection schedule, well, startups are offering trash service at the doorstep. A third-party developer helped Alipay build a recycling mini app and is now collecting garbage from 8,000 apartment complexes across 11 cities. To date, two million people have sold recyclable materials through its platform.

Besides helping households out, companies are also building software to make property managers, life easier. Some residential complexes in Shanghai began using QR codes to trace the origin of garbage. This way, regulators in the region know exactly which family has produced the trash and fine violators.

1.What are some residents confused about?

A.Environmental knowledge. B.Bin for dog poop.

C.Some waste classification. D.Time for dumping.

2.What is the advantage of trash service at the doorstep?

A.It provides time flexibility. B.It reduces household waste.

C.It saves people from typing. D.It classifies rubbish properly.

3.Who will probably most welcome the use of QR codes?

A.Third-party developers. B.Company managers.

C.Community administrators. D.Rubbish collectors.

4.What is the main idea of this article?

A.People need recycling apps badly.

B.People should classify their rubbish.

C.How regulators benefit from the tech.

D.How China uses tech to sort waste.