ROOMMATES

FEMALE ROOMMATE

WAMTED: Own room near campus. Available December 1st. Rent $300 per month until March 1st. $450 thereafter. Call Jill for details, 800-7839.

MEED PERSON to assume lease for own bedroom in apt. near campus, $’380/mo. starting Jan. 1st. Call 800-6157 after 5p.m..DOMESTIC SERVICE

EARLY HOUR WAKE-UP SERVICE: For prompt, courteous wake-up service, call 800-0760.

HELP WANTED

BABYSLTTER—MY HOME If yoare available a few hours during the day, and some evenings to care for 2 school-age children, please call Gayle Moore, days 800-1111, evenings and weekends 800-4964.

PERSONS WANTED for delivery work, Own transportation. Good pay. Apply 2311 E. Stadium. Office 101, after 9 a.m.

TELEPHONE RECEPTIONIST WAMTED. NO experience necessary. Good pay. Apply 2311 E. Stadium. Office 101, after 9 a.m.

WAITRESS WANTED: 10 a.m.-2 p.m. or 10:30 a.m.-5 p.m. Apply in person. 207 S. Main, Curtis Restaurant.

HELP WANTED for house cleaning 1/2 day on weekends. When----to be discussed for mutual convenience. Good wages. Sylvan Street. Call 800-2817.

45. Where will yopost a notice if yoneed someone to look after your children?

A.PERSONAL B.HELP WANTED C.DOMESTIC SERVICE D.ROOMMATES

46. A second-hand jacket will probably cost yo.

A. $60 B. $40 C. $20 D.10

47. To have your travel notes published, yomay contact .

A. Students’ Union B. Gayle Moore

C. The International Center D. Life Planning Workshop

48. If yowant to have someone wake youp in the morning, yomay call .

A.800-5224 B.800-5770 C.800-7839 D.800-0760

C

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 insects, 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 detest 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 that can house thousands of plants.

The research team worked with an e-nose that 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 the 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 Dudareve, 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.

49. 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

50. What did the scientists do to find out if the e-nose worked?

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.

51. According to the writer, the most amazing thing about the e –nose is that it can ______.

A. pick out ripe fruits

B. spot the insects quickly

C. distinguish different damages to the leaves