题目内容
---- The exam was too difficult, wasn’t it?
---- Yes, ______ could not pass it.
| A．somebody | B．anybody | C．nobody | D．everybody |
D
解析
Plants can’t communicate by moving or making sounds, as most animals do. Instead, plants Produce volatile compounds, chemicals that easily change from a liquid to a gas. A flower’s sweet smell, for example, comes from volatile compounds that the plant produces to attract insects such as Bugs and bees.
Plants can also detect volatile compounds produced by other plants. A tree under attack by Hungry insets, for instance, may give off volatile compounds that let other trees know about the Attack. In response, the other trees may send off chemicals to keep the bugs away ——or even Chemicals that attract the bugs’ natural enemies.
Now scientists have created a quick way to understand what plants are saying: a chemical Sensor（传感器）called an electronic nose. The “e-nose” can tell compounds that crop plants make When they’re attacked Scientists say the e-nose could help quickly detect whether plants are being Eaten by insects. But today the only way to detect such insects is to visually inspect individual Plants. This is a challenging task for managers of greenhouses, enclosed gardens than can house Thousands of plants.
The research team worked with an e-nose than recognizes volatile compounds. Inside the device, 13 sensors chemically react with volatile compounds Based on these interactions, the e-nose gives off electronic signals that the scientists analyze using computer software.
To test the nose, the team presented it with healthy leaves from cucumber, pepper and tomato plants, all common greenhouse crops. Then scientists collected samples of air around damaged leaves from each type of crop, These plants had been damaged by insects, or by scientists who made holes in the leaves with a hole punch（打孔器）. The e-nose, it turns out, could identify healthy cucumber, pepper and tomato plants based on The volatile compounds they produce, It could also identify tomato leaves that had been damaged. But even more impressive, the device could tell which type of damage ---- by insects or with a hole Punch ---- had been done to the tomato leaves.
With some fine-tuning, a device like the e-nose could one day be used in greenhouses to quickly spot harmful bugs, the researchers say. A device like this could also be used to identify fruits that are perfectly ripe and ready to pick and eat, says Natalia Dudareva, a biochemist at Purdue University in West Lafayette, Ind. who studies smells of flowers and plants. Hopefully, scientists believe, the device could bring large benefits to greenhouse managers in the near future.
【小题1】We learn from the text that plants communicate with each other by____.
| A．making some sounds | B．waving their leaves |
| C．producing some chemicals | D．sending out electronic signals |
| A．They presented it with all common crops. |
| B．They fixed 13 sensors inside the device. |
| C．They collected different damaged leaves. |
| D．They made tests on damaged and healthy leaves. |
| A．pick out ripe fruits |
| B．spot the insects quickly |
| C．distinguish different damages to the leaves |
| D．recognize unhealthy tomato leaves |
| A．is unable to tell the smell of flowers |
| B．is not yet used in greenhouses |
| C．is designed by scientists at Purdue |
| D．is helpful in killing harmful insects |
The E-mail Jack had looked forward to ______ last night at last and he was very happy.
|
A．arrived |
B．arriving |
C．had arrived |
D．arrived |