A Plant Enemy"s Enemy etc.

Plants have to stand their ground when pests attack. Theres simply no running away. Some plants play defense， using prickly thorns， thick bark or even bitter tastes to ward off insects and other attackers. But for many plants， the best defense is a good offense. These plants - including some varieties of corn and cotton - call for help. And predatory critters frequently respond， arriving to prey on the plants attackers.

Of course， plants dont literally scream out to those helpers. Instead， they produce chemicals known as volatiles. Such chemicals easily evaporate and travel on the wind. The odor of these vapors silently attracts insects or other helpers - organisms that scientists call "bodyguards".

Bodyguard critters eat the pests that eat plants. So if plants have enemies， then bodyguards are enemies of the plants' enemies.

Plants evolved the ability to produce these chemical distress calls long ago. Scientists only discovered this secret signaling， however， in 1988. Since then， researchers have been probing how plants use these chemicals to communicate with animals. Their surprising findings have begun helping farmers boost the amount of crops they produce - and they do it with less need for toxic pesticides.

植物天敌的天敌

植物受到害虫攻击时无法逃离，只能呆在原地。有些植物凭借荆棘、厚皮甚至苦味来驱走害虫和其他攻击者，达到保护自身的目的。但对于许多植物来说，最佳防御手段是强有力的进攻。此类植物，包括玉米、棉花的某些品种，它们会发出求救信号，害虫的天敌通常会作出回应，前来捕杀攻击植物的害虫。

当然，植物不是真的向救援者发出尖叫声，而是释放出具有挥发性的化学物质。该化学物质很快蒸发，并随风飘散。蒸发雾气的气味会悄然引来昆虫或其他救援者，科学家将这些救援者称为“保镖”。

被称为“保镖”的小动物会吃掉吃植物的害虫，所以，如果植物有天敌，那么植物保镖是植物天敌的天敌。

很久以前，植物在进化过程中就已经获得了这种释放化学物质来求救的能力，但是科学家在1988年才发现了这种秘密求救信号。自那以后，研究者们开始探究植物怎样利用化学物质与动物交流，他们惊人的研究发现已经开始用于帮助农民增加作物的产量，并且帮助农民们减少了对有毒杀虫剂的依赖。

（注意斜体字的译法）

If your wallet's starting to get a little too thick to fit in your pocket， a new gadget named Coin might be able to lighten your load. Remember， it's Coin， not coins.

It looks no different than a standard （1） c card， but is actually a small （2） d that can act as a credit card， debit card or gift card. The device is available for pre-order and expected to start shipping this summer.

Coin CEO Kanishk Parashar said that the company was born from the ashes of the failed company Smart Market. Coin isn't another system of （A） p ， but Parashar's way of uniting several different （3） m of payment into a single device. Coin users plug a magnetic strip reader into a smartphone， swipe heir cards， and sync their information through the company's app.

In order to make a payment， users tap a button on the Coin card and pick which account they want to pay with， whether it's a business credit card or a personal debit card. After picking an account， the Coin card is swiped through， no different than any other card.

It may seem a little risky to keep all your financial accounts bound to a single card. However， Parashar and his colleagues have engineered （B） s measures into Coin. All communication between the Coin card， app and servers are heavily encrypted. "All your financial information would be secured，" said Parashar.

In addition， Coin cards themselves broadcast a low-power Bluetooth signal that （C） d where your smartphone is. "It works on the concept of being on a leash，" said Parashar. "If you're walking away from your card and go out of range of the Bluetooth， your phone will then set an （4） a ."

But even if you miss that alert， you don't have to worry about other people using your card. After a certain period of time （determined by the user）， Coin will automatically deactivate and stop other p________ （people） from using it.

（A， B， C， D FOR CROSS， 1， 2， 3， 4 FOR DOWN. The first letters of the absents were given）

Horse Friends - Math Puzzle

Three horses are standing in a triangular field， which is exactly 100 yards on each side. One horse stands at each corner； and simultaneously all three set off running. Each horse runs after the horse in the adjacent corner on his left， thus following a curved course， which terminates in the middle of the field， all three horses arriving there together. The horses obviously ran at the same speed， but just how far did they run？