Hurricane (飓风) Katrina

A．hurricane is a fiercely powerful, rotating (旋转的) form of tropical storm that can be 124 to 1, 240 miles in diameter. The term hurricane is derived from Hurican, the name of a native American storm god. Hurricanes are typical of a calm central region of low pressure between 12 to 60 miles in diameter, known as the eye. They occur in tropical regions. Over its lifetime, one of these storms can release as much energy as 10,000 nuclear bombs.
The seed for hurricane formation is a cluster (聚焦) of thunderstorms over warm tropical waters. Hurricanes can only form and be fed when the sea-surface temperature exceeds 27℃ and the surrounding atmosphere is calm. These requirements are met between June and November in the northern part of the world.
Under these conditions, large quantities of water evaporate (蒸发) and condense (冷凝) into clouds and rain-releasing heat in the process. It is this heat energy, combined with the rotation of the Earth, that drives a hurricane.
When the warm column of air from the sea surface first begins to rise, it causes an area of low pressure. This in turn creates wind as air is drawn into the area. This spinning wind drags up more moist air from the sea surface in a process that strengthens the storm. Cold air falls back to the ocean surface through the eye and on the outside of the storm.
Initially, when wind speeds reach 23 miles per hour, these mild, wet and grey weather systems are known as depressions, or low air pressure. Hurricane Katrina formed in this way over the south-eastern Bahamas on 23 August 2005. Katrina has had a devastating impact on the Gulf Coast of the US, leaving a disaster zone of 90,000 square miles in its wake (尾迹)—almost the size of the UK. Thousands have been killed or injured and more than half a million people have become homeless in a humanitarian (人道主义的) crisis of a scale not seen in the US since the Great Depression. The cost of the damage may top $100 billion.
The word "impact" (paragraph 5) could be best replaced by

A．Critical.

B．Hostile.
C．Objective.

D．Enthusiastic.

A credit card that will not work unless it hears its owner’s voice could become an important weapon in the fight against fraud (欺骗).
The card requires users to give a spoken password that it recognizes using a built-in voice-recognition chip. The idea is to prevent thieves using a stolen card or fraudsters using someone else’s credit card details to buy goods online.A model built by engineers at Beepcard in Santa Monica, California, represents the first attempt to pack a microphone, a loudspeaker, a battery and a voice-recognition chip into a standard-sized credit card.
They are not quite there yet: the card is the length and width of an ordinary credit card, but it is still about three times as thick. The company now plans to make it thinner.
The voice card is based on an earlier Beepcard technology designed to prevent fraud in online transactions. This earlier card has no microphone, but has a built-in loudspeaker that it uses to "squawk" (发出叫声) a voice ID signal via a computer’s microphone to an online server.
By verifying (证实) that the signal matches the card details, the server can establish that the user is not simply keying in a credit card number but actually has the card to hand. The ID code changes each time the card is used in a pre-ordered sequence that only the server knows.
This prevents fraudsters recording the beeps, noting the card details and then playing back the audible ID when they key in the details later. But this earlier technology cannot prevent fraudulent use of stolen cards. The new one can.
The new voice card also identifies itself by its ID squawk, but it will not do this until it has verified the legitimate (合法的) user’s spoken password. Thieves will be unable to use the card because even if they knew the password they would have to be able to copy the owner’s voice with a high degree of accuracy.
The challenge for Beepcard has been to develop voice-recognition and audio circuitry that can be powered by a mini battery embedded (潜入的) in a credit card. To maximize battery life, the electronics are only switched on when the card is being used. Pressing a button on the card’s surface prompts it to utter "Say your password" in female voice. If the voice-recognition software proves that the password is authentic (真实的), it sends its ID squawk which the server then identifies, allowing the transaction to proceed.