Problem: Washington (CNN) -- The U.S. Food and Drug Administration announced Wednesday that laboratory tests on popular smoking devices known as electronic cigarettes have found they contain carcinogens and other toxic chemicals dangerous to humans. E-cigarettes are battery-operated and contain cartridges filled with nicotine and other chemicals. Known as "e-cigarettes," the devices are battery-operated and contain cartridges filled with nicotine and other chemicals, spiced with flavors such as chocolate, cola or bubble gum. While manufacturers tout e-cigarettes as a "healthy way" to smoke, federal health officials say the devices turn nicotine, which is highly addictive, and other chemicals into a vapor that is inhaled by the user. "The FDA is concerned about the safety of these products and how they are marketed to the public," said Dr. Margaret A. Hamburg, commissioner of the FDA. CNN contacted Florida-based Smoking Everywhere, one of the largest manufacturers of e-cigarettes, after the FDA announcement, and a spokeswoman said the company had no comment. Because e-cigarettes have not been submitted to the FDA for evaluation or approval, the agency had no way of knowing the levels of nicotine or the amounts or kinds of other chemicals that the various brands of these products deliver to the user. That is why the FDA began to test them. The FDA's Division of Pharmaceutical Analysis analyzed the ingredients in a small sample of cartridges from two leading brands of e-cigarettes. In releasing its information, the FDA did not identify the two companies, but said in one sample, diethylene glycol -- a chemical used in antifreeze that is toxic to humans -- was detected. Other samples detected carcinogens that are dangerous to those who smoke them, the FDA said. The FDA has been examining and seizing shipments of non-U.S.-made e-cigarettes at the U.S. border since summer 2008. To date, 50 shipments have been stopped. The products examined thus far meet the definition of a combination drug-device product under the Federal Food, Drug, and Cosmetic Act. "We know very little about these devices, said Dr. Jonathan Samet, director of the Institute for Global Health at the University of Southern California, "but to say they are healthy -- that's highly doubtful."

Question: "Describe some characteristics of e-cigarettes."

Answer: "They are battery operated, have nicotine and are flavored"
Answer: yes

Problem: Plants also detect the daily cycle of light and darkness. Do you know how plants respond to these changes? Some plants open their leaves during the day. It is during these hours the plant can collect sunlight. At night, the plant closes its leaves to prevent water loss. Many plants respond to the change in the length of the day. As days grow shorter, some plants respond by going dormant. Dormant is when a plant suspends its growth. It does this in order to survive. Shorter days signal the coming of winter. Winter in most areas means extreme cold. It is also very dry in the winter months. As winter approaches, some plants respond by their leaves changing color. After the change in color, they fall off. This dormancy period helps trees. It allows them to survive the cold and dry winter. Plants only want to grow when conditions are right.

Question: "Why do plants close their leaves at night?"

Answer: "So they don't die in the nighttime chill"
Answer: no

Problem: A flood occurs when a river overflows its banks. This might happen because of heavy rains. Floodplains In very flat regions, flood water may spread out on the surface of the land. It then slows down and drops its sediment. If a river floods often, a floodplain develops. A floodplain is an area where a thick layer of rich soil is left behind as the floodwater recedes. Thats why floodplains are usually good places for growing plants. They are very flat areas and they have very rich soils. The Nile River valley is a great example of a floodplain. Each year, the Nile River rises over its banks. This floodwater carries a lot of sediment. This sediment has been eroded off areas of land from upstream. This sediment is dropped as the water slows down after spreading across the land. What is left behind is a very rich soil. Thats why crops can be raised in the middle of a sandy desert. Natural Levees A flooding river often forms natural levees along its banks. A levee is a raised strip of sediments deposited close to the waters edge.

Question: "Where does the sediment in a flooding river come from, and where does it eventually come to rest?"

Answer: "Sandy dessert"
Answer:
no