For many years, in the desert camels were the only kind of transport. Before the age of modem trains, camel trains carried all the things between Central Asia and Europe. People made camel trains with 10,000 to 15,000 animals. Each camel could carry approximately 200 kilos and could travel twenty miles a day. This kind of transport was so important that people called camels the ‘ships of the desert’
Перевод текста будет доступен здесь.
Сравнение временных форм Indefinite, Continuous, Perfect и Perfect Continuous в английском языке.