People in the US can now carry an artificial intelligence （AI) around in their pocket, whe

People in the US can now carry an artificial intelligence (AI) around in their pocket, where it waits patiently to be told what to do.

Siri, an iPhone application that understands spoken commands and uses the web to carry them out,is a byproduct from a US military project to develop an artificially intelligent assistant.

Many people's experience of a "virtual assistant" may be limited to Microsoft's annoying classic Mr. Clippy. But in the week we spent together, my AI assistant has performed admirably in finding me restaurants, or the location of the nearest coffee shop. It wasn't even stumped when I asked "do I need my umbrella today？" coming straight back with the local weather forecast.

A typical command might be: "Reserve a table for two at a good French restaurant in San Francisco." Siri responds by presenting a list of top-rated restaurants that can be booked on OpenTable.com. If you say which time you want, it can book you a table without your lifting a finger.

In some ways Siri is just a fancy front-end to the 35 sites it can connect to, from taxi booking sites to movie review databases. But what's new is the way it can interpret the intentions of its master or mistress and use those sites to put them into action.

Doing that requires the ability to actually understand the meaning of words you use, not just passing on keywords blindly, says Siri co-founder Adam Cheyer.

"Book a four-star restaurant in Boston seems pretty straightforward," says Cheyer, "until you realise that Book is a city in the US, and Star is also a city in the US, and there are 13 Bostons, and Star is also the name of a restaurant."

To cut through what Cheyer calls the "combined explosion of interpretations", Siri uses your location, and the history of the commands you've given. It knows that "book" is most likely a command verb, unless you happen to be near the city of Book.

Siri attaches probabilities to the interpretation of each word and cross-reference(参照) with your location and other data, some of which you must provide yourself.

According to the passage, Siri is most probably ______.

A．still at its experimental stage

B．very popular with iPhone users

C．a US military assistant software

D．an artificial intelligence software