25 Choose pair or piece to complete the sentences. 1. Sara bought a new (pair/piece) pair of leggings yesterday. 2. Can I have a (pair/piece) of paper to write a note? 3. Mum usually has a (pair/piece) of sugar with tea. 4. James was choosing a (pair/piece) of shorts when he saw Bob. 5. This (pair/piece) of jeans is blue. 6. My uncle gave me a big (pair/piece) of land for gardening. 7. Mike should finish this (pair/piece) of work today. 8. This (pair/ piece) of scissors is very sharp. 9. Sam was very hungry and took another (pair/piece) of cheese from the plate. 10. We need another (pair/piece) of hands to do the work.

1. pair

2.piece

3.piece

4.pair

5.pair

6.piece

7.piece

8.pair

9.piece

10.pair

Объяснение:

pair - пара, или со словом вроде джинсы , ножницы, шорты, которое всегда во множественном ; piece - кусок, часть

Today the word "electronics" is the general usage.
The center of this world is a tiny silicon plate of a few square millimeters, an integrated circuit, or a chip, as it is more commonly known. The integrated circuit is undoubtedly one of the most sophisticated inventions of man, science and technology. As the operation os an integrated circuit depends on microscopic "components", the purity of all materials and the cleanness at the plant they are produced at must be of the highest quality. 
In the past it took scientists and reserchers a whole lifetime to make a few thousand calculations, whereas for a modern computer this task is a matter of a few seconds. At present computers capable of performing billions of operations a second are required. In the next few years engineers will complete the work on computers of above 2 billion operations a second. It will take a few more years to produce a 10-billion operationscomputer. According to some researchers, we are close to what can be regarded as a true physical limit. But other specialists think that photons will make the operation a thousand times faster. This means that in the future it will be possible to expect the appearance of photon computers and that computations will be done by means of light. In a few decades a new age of light may replace the stil youthful electronic age. The race is going on.

1. Air-conditioning system in a railway car ensures a constant supply of fresh air in hot weather and heating the entire saloon in cold weather, doesn`t it?

2. The Trans-Siberian Railway is divided into six railways in Ural, Siberia and the Far East, didn`t it?

3. George Pullman became well known for luxury sleeping cars called Pullman cars in his honour, didn`t he?

4. These express trains will proceed to the final destination without any stops, won`t they?

5. Both direct and alternating current can be used on electrified railways, can`t they? 

6. Powerful track-laying machines have been developed for the building of railroads, haven`t they?