Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions.

          Although speech is the most advanced form of communication, there are many ways of communicating without using speech. Signals, signs, symbols, and gestures may be found in every known culture. The basic function of signal is to impinge upon the environment in such a way that it attracts attention, as, for example, the dots and dashes of a telegraph circuit. Coded to refer to speech, the potential for communication is very great. Less adaptable to the codification of words, signs also contain meanings in and of themselves. A stop sign or a barber pole conveys meaning quickly and conveniently. Symbols are more difficult to describe than either signals or signs because of their intricate relationship with the receiver's cultural perceptions. In some cultures, applauding in a theater provides performers with an auditory symbol of approval. Gestures such as waving and handshaking also communicate certain cultural messages.
          Although signals, signs, symbols, and gestures are very useful, they do have a major disadvantage in communication. They usually do not allow ideas to be shared without the sender being directly adjacent to the receiver. Without an exchange of ideas, interaction comes to a halt. As a result, means of communication intended to be used for long distances and extended periods must be based upon speech. Radio, television, and the telephone are only a few

Which of the following would be the best title for the passage?

A. Speech  

B. Gestures  

C. Communication         

D. Signs and signals

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the following questions

The principle of use and disuse states that those parts of organisms' bodies that are used grown larger. Those parts that are not tend to wither away. It is an observed fact that when you exercise  particular muscles, they grow. Those that are never used dimish. By examining a man's body, we can tell which muscles he uses and which he doesn't. We may even be able to guess his profession or his reaction. Enthusiasts of the "body- building" cult make use of the principle of use and disuse to "build" their bodies, almost like a piece of sculpture, into whatever unnatural shape is demanded by fashion in this peculiar minority culture. Muscles are not the only parts of the body that respond to use in this kind of way. Walk barefoot and you acquire harder skin on your soles. It is easy to tell a farmer from a bank teller by looking at their hands alone. The farmer's hands are horny, hardened by long exposure to rough work. The teller's hands are relatively soft.

The principle of use and disuse enables animals to become better at the job of surviving in their world, progressively better during their lifetime as a result of living in that world. Humans, through direct exposure to sunlight, or lack of it, develop a skin color which equips them better to survive in the particular local conditions.

Too much sunlight is dangerous. Enthusiastic sunbathers with very fair skins are susceptible to skin cancer. Too little sunlight, on the other hand, leads to vitamin-D deficiency and rickets. The brown pigment melanin which is synthesized under the influence of sunlight, makes a screen to protect the underlying tissues from the harmful effects of further sunlight. If a suntanned person moves to a less sunny climate, the melanin disappears, and the body is able to benefit from what little sun there is. This can be represented as an instance of the principle of use and disuse: skin goes brown when it is "used", and fades to white when it is not.

The word "susceptible" could be best replaced by………. 

A. vulnerable

B. condemned  

C. allergic 

D. suggestible

wa......wa......................!!!!!!!!!!!!!!!!

a)  \(\left(x-21\right)^3-7=2^2.5\)  
     \(\left(x-21\right)^3=4.5+7=27\)
     \(\left(x-21\right)^3=3^3\)
     \(\Rightarrow x-21=3\Rightarrow x=24\)

Gọi số cần tìm là ab.Theo bài ra ta có:

a0b=7xab

=>a00+b=7x(a0+b)

=>100xa+b=7x(10xa+b)

=>100xa+b=70xa+7xb

=>100xa-70xa=7xb-b

=>30xa=6xb

=>5xa=b

xét a=1=>b=5=>ab=15

xét a=2=>b=10(loại)

Vậy số cần tìm là 15