Most mothers have a good piece of advice: Never go into a supermarket hungry! If you go shopping for food before lunchtime, you'll probably buy more than you plan to. Unfortunately, however, just this advice isn't enough for consumers these days. Modem shoppers need an education in how and how not to buy things at the grocery store. First, you should check the weekly newspaper ads, find out the items that are on sale and decide if you really need those things. In others words, don't buy anything just because it's cheaper than usual! "New and Improved!" or "All Natural" on the front of a package influence you. Instead, read the list of ingredients (成分) on the back. Third, compare prices; that is, you should examine the prices of both different brands and different sizes of the same brand.
Another suggestion for consumers is to buy generic (普通的) items instead of famous brands. Generic items in supermarkets come in plain packages. These products are cheaper because manufacturers don't spend much money on packing or advertising. The quality, however, is usually identical to the quality of well-known name brands. In the same way, in buying clothes, you can often find high quality and low prices in brands that are not famous. Shopping in discount clothing stores can help you save a lot of money. Although these stores aren't very attractive, and they usually do not have individual dressing rooms, not only are the prices low, but you can often find the same famous brands that you find in high-priced department stores.
Wise consumers read magazine advertisements and watch TV commercials, but they do this with one advantage: knowledge of the psychology behind the ads. In other words, well-informed consumers watch for information and check for misinformation. They ask themselves questions: Is the advertiser hiding something in small print at the bottom of the page？ Is there any real information in the commercial, or is the advertiser simply showing an attractive image？ With the answers to these questions, consumers can make a wise choice.
In the above passage, the author's main purpose is to ______.

A. suggest consumers to buy generic items instead of fatuous brands
B. give some pieces of advice to consumers
C. convince readers that the advice of most mothers isn't enough for consumers these days
D. persuade consumers not to believe the advertisements