Помогите перевести предложения,обратив внимание на время .
1. Farmers did not know much about nutrients in the 17 yh century.
2.After Columbus had discovered America he brought some new varietes of plants to Europa .
3. In 1870 Pavlov entered the University of St.Petersburg where he studied chemistry and physiology .
4. The milk yields have fallen and some animals have become sick.
5.Scientists are going to continue their research in the field of animal nutrition .
6. Nowadays farmers are trying to satisfy the peoples requirements in highly nutritive products.
7. In the past,farmers had much difficulty in feeding cattle during the winter season
8. Two centuries ago farmers used their own practical experience to satisfy animals with feeds .
9. Farmers often produce high-quality butter and cream from milk.
10. Farmers will rely on the record of an individual animal`s ancestors .
11. Chemical genetics remains a basis for all other topics in genetics
12 . At present farmers are using different breeding programmes to improve their herds.
13. They will have returned before you come home.
14. Before the dog attacks a potential enemy ,it will show signs of hostility .
15. Recently ,several organizations have established conservation programmes for endangered domestic breeds of cattle ,sheep and swine .
16. When the weather is rainy,windy and cold,cattle will decrease the grazing time and drink little water.
17. Many naturalists have studied aspects of animal behaviour through the centuries .
18. In 1949 Frisch established that bees use the sun as a compass.
19. Poor preventive measures have resulted in a rapid spread of infection among sheep .
20. If farmers apply modern cultivation practices ,yields of forage crops will be higher.
Объяснение:
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