شرکت در آزمون آنلاین زبان انگلیسی 1 - زبان انگلیسی 1 | آزمون شماره 13475

You ................... be tired because you have worked very hard.

Sanctions stop us to have a good ................................... with other countries in all aspects .

The average human adult has more than 5 liters (6 quarts) of blood in his or her body. Blood carries oxygen and food to living cells and takes away their rubbish. It also gives safe cells to fight diseases and contains platelets that can form a plug in a damaged blood vessel to stop blood loss.

Through the circulatory system, blood adapts to the body's needs. When you are exercising, your heart pumps harder and faster to provide more blood and also oxygen to your muscles. During an illness, the blood gives more white cells to the site of disease, where they gather to fight and kill the harmful microbes.

All of these functions make blood a valuable liquid. Each year in the USA, 30 million units of blood are transfused to patients who need them. Blood is considered to be so valuable that it is also called "red gold" because the cells and proteins it contains can be sold for more than the cost of the same weight in gold.

The underlined phrase “safe cells” in paragraph 1 refers to … .

Ciphers are easy to use and remember. A simple cipher, however, is also easy to break. In any language, some letters are used more than others. In English, “e” is the most common letter, followed by “t” and “a”. Some letters frequently occur together, such as th and ch. By studying several messages, a code breaker can easily figure out a simple cipher. Complex ciphers use a different cipher, or code, for each letter in a message. The letters in a keyword reveal which cipher is used for each letter. Only people who know the keyword can read the message. Codes can be almost unbreakable if they use combinations of ciphers and change the keyword often.

During World War II (1939-1945), math experts in Britain broke the German military codes. Britain was at war with Germany. German military forces coded messages with a device called an Enigma machine. Enigma used gears and wheels to create millions of different ciphers. But British mathematicians and code breakers figured out the cipher and uncovered German military plans.

The word “Cipher” in line 1 is closest in meaning to a/an … .

Tina and Shelly … to the hotel when it … to rain .