The correct answer is A) they were more worried about each other than Arabian desert traders.
The reason why the Byzantines and Sasanians more o less left Arabian alone was because they were more worried about each other than Arabian desert traders.
The first Arab tribes appeared around 200 CE in the Syrian Desert. They went to the Arabian peninsula around 630 CE. In that time, the Sabaean kingdom controlled the coast of Eastern Arabia. Between 7 and 11 AD, the Byzantine empire wage war with Arab muslims that started to conquer territories that belonged to the Byzantine empire such as Egypt and Syria. Indeed, the Arabs besiege Constantinople two times. Constantinople was the capital city of the Byzantine Empire. But at the end, the Byzantine army defeated the Arabs.