烤烟打顶抹杈有哪些作用？
参考答案：
（1）促进根系发育，打顶抹杈可促进次生根的萌发，增加根的深度和密集度，也增强了烟碱的合成，叶内烟碱含量得到提高。
（2）扩大叶片，增加干物质积累，打顶抹杈后，各部位叶片都有所增大，尤以顶叶更明显；同时可以增加叶面积和单位面积重量。
（3）增加养分吸收，在花前打顶，能促进烟株对一些养分的吸收，促进烟株圆顶。
（4）调控烟株的长势长相，生产上可以通过控制打顶早和打顶高度，调控烟株吸入养分数量，进行控制烟株后期的长势和株型。
（5）减轻病虫害：打顶抹杈增强了田间通风透光，降低了烟棵之间的空气湿度；同时去掉了烟芽赖以生成的幼嫩组织，从而减少了虫害和依靠烟芽传播的病毒病害。
Passage Two
| In 1998 consumers could purchase virtually anything over the Internet. Books, compact discs, and even stocks were available from World Wide Web sites that seemed to spring up almost daily. A few years earlier, some people had predicted that consumers accustomed to shopping in stores would be reluctant to buy things that they could not see or touch in person. For a growing number of time-starved consumers, however, shopping from their home computer was proving to be a convenient alternative to driving to the store. A research estimated that in 1998 U.S. consumers would purchase ＄ 7.3 billion of goods over the Internet, double the 1997 total. Finding a bargain was getting easier, owing to the rise of online auctions and Web sites that did comparison shopping on the Internet for the best deal. For all the consumer interest, retailing in cyberspace was still a largely unprofitable business, however. Internet pioneer Amazon. com, which began selling books in 1995 and later branched into recorded music and videos, posted revenue of $153.7 million in the third quarter, up from ＄ 37.9 million in the same period of 1997．Overall, however, the company’s loss widened to ＄ 45.2 million from $ 9.6 million, and analysts did not expect the company to turn a profit until 2003．Despite the great loss, Amazon com had a stock market value of many billions, reflecting investors’ optimism about the future of the industry. Internet retailing appealed to investors because it provided an efficient means for reaching millions of consumers without having the cost of operating conventional stores with their armies of salespeople. Selling online carried its own risks, however. With so many companies competing for consumers’ attention, price competition was intense and profit margins thin or nonexistent. One video retailer sold the hit movie Titanic for ＄ 9.99, undercutting (削价) the ＄19.99 suggested retail price and losing about ＄ 6 on each copy sold．With Internet retailing still in its initial stage, companies seemed willing to absorb such losses in an attempt to establish a dominant market position. |
It can be inferred from the passage that Amazon. com______.
A．is making a profit now
B．will probably make a profit in 2003
C．is a company that sells books only
D．suffers a great loss on the stock market