Air pollution is a big problem for cities in most countries． Many people are dying from it． But how can we tell the air quality is good or bad？

    On a tree next to a river in Amsterdam， a tiny birdhouse glows （发光） bright green when the air is clean． If you're standing nearby， the birdhouse will also give you a free Wi﹣Fi connection﹣but only if pollution level is low enough． The designer is Joris Lam． His birdhouse tells you about the air quality．

    Joris' birdhouse is called TreeWifi． It can be put on a tree around your house to test the air quality． People can see a screen with information about the local air quality and how to improve it． TreeWifi is a simple way for people to know about the air pollution around them． If the birdhouse does not glow， people should care more about the environment． It reminds them to change their lifestyles． For example， to protect the air， they can ride bikes or just walk instead of driving cars．

    "Imagine if trees gave free Wi﹣Fi， people would plant more trees like crazy． It's a pity that they only give us the oxygen（氧气） we breathe，" Joris said．

    The birdhouse doesn't work as a home for birds now． Joris and his team are trying to make some changes to it． In the future， they hope birds will live in the birdhouse and the heat of its green light will be used to keep birds warm in winter．

（1）What does the underlined word "it" in Paragraph 1 refer to？　　

A． The birdhouse．

B． Air quality．

C． Air pollution．

（2）People can get a free Wi﹣Fi connection when　　．

①people are standing nearby

②the pollution level is low enough

③the air quality is low enough

A．①②

B．②③

C．①③

（3）Joris designed a screen for the birdhouse to　　．

A．receive the free Wi﹣Fi connection

B．protect the birdhouse from the rain

C．show information about the air quality

（4）In the future， the birdhouse will also be used　　．

A． as a home for birds

B． to tell us the weather

C． to give us the oxygen