Прочитайте текст. Запишите в поле ответа цифру 1, 2, 3 или 4, соответствующую выбранному вами варианту ответа.
The international convention stated that each station should have a unique call sign because …
- both ship and land practiced to begin their messages with short identifiers.
- sometimes users chose call signs that had already been chosen.
- radio was used as a wireless telegraph.
- it was necessary to shorten the number of dots and dashes needed to identify each station.
Ответ: 2