我们正在计算的是该质点的瞬时加速度。 __________ we are calculating is the instantaneous acceleration of the particle.

Universal Product Code

What are the zebra stripes (See the figure) on the Instant Mashed Patato Flakes package? They are special black and white vertical lines. These black and white stripes can be read by an optical scanner, or computer. The "scanner", which reads the lines of code, is a small laser beam of light. When the light rays is broken by the black stripes, the computer "reads" the information about the product.

This code is called the Universal Product Code (UPC). It is designed to add speed and efficiency to stores by using computers. It can do this in several ways. First, it is not necessary for workers to put individual prices on items. By using UPC, the computer can print out the accurate price of the item. Errors in prices are eliminated, or done away with. Also, the time spent checking out is reduced UPC gives an itemized receipt to the customer with all the items, prices, and totals. The store clerk does not need to spend time checking the price on the item and punching it into the cash register. This UPC computerized system will probably save as much as 45 percent of the checkout clerk's time.

What do the stripes mean? How does the computer interpret the stripes? The number printed below the vertical bars identifies the manufacturer and the manufacturer's item. As many as 10 trillion individual machine-readable numbers can be used with this system. In the example, the 0 on the left side means that it is a grocery item. The numbers 36800 indicate the manufacturer, in this case it is the Food Club Company. The last five digits, 51512, mean it is a pack of mashed patato flakes. The light rays from the light beam read these lines, and the message is sent directly to the computer. The computer then finds the information about this product (price, inventory data) and sends it instantly back to the terminal at the checkout counter. At the same time, it keeps an inventory for the store manager. Many products have labels with these stripes.

The figures printed below the stripes are codes of the producer and the product.

A．right

B．wrong

C．Doesn't say

Did you know that all human beings have a "comfort zone" regulating the distance they stand from someone when they talk? This distance varies in interesting ways among people of different cultures.

Greeks, others of the Eastern Mediterranean, and many of those from South America normally stand quite close together when they talk, often moving their faces even closer as they warm up in a conversation. North Americans find this awkward and often back away a few inches. Studies have found that they tend to feel most comfortable at about 21 inches apart. In much of Asia and Africa, there is even more space between two speakers in conversation. This greater space subtly lends an air of dignity and respect. This matter of space is nearly always unconscious, but it is interesting to observe.

This difference applies also to the closeness with which people sit together, the extent to which they lean over one another in conversation, how they move as they argue or make an emphatic(强调的)point. In the United States, for example, people try to keep their bodies apart even in a crowed elevator; in Pads they take it as it comes!

Although North Americans have a relatively wide "comfort zone" for talking, they communicate a great deal with their hands—not only with gesture but also with touch. They put a sympathetic hand on a person's shoulder to demonstrate warmth of feeling or an arm around him in sympathy; they nudge (用肘轻碰)a man in the ribs to emphasize a funny story; they pat an arm in reassurance or stroke a child's head in affection; they readily take someone's arm to help him across a street or direct him along an unfamiliar route. To many people— especially those from Asia or the Moslem countries—such bodily contact is unwelcome, especially if inadvertently(不经意地)done with the left hand.

A suitable title for this passage would be ______.

A．Body Language

B．Distance And Bodily Contact

C．Cultural Differences

D．Hand Signals

Real-time trading in foreign markets and instantaneous currency conversion will become possible in the near future．（ ）

I wanted to build a bookcase, but I could not make. ______ of the instructions.

A．understanding

B．sense

C．reality

D．sight