本题考查罗马带到英国的宗教是什么。

The Romans also brought the new religion, Christianity, to Britain. This came at first by indirect means, probably brought by traders and soldiers, and was quite well-established before the first Christian Emperor, Constantine, was proclaimed in AD 306.

罗马人还把基督教这一新宗教带到不列颠，最初很可能是由商人和士兵间接传入的。公元306年第一位基督教皇帝，君士坦丁大帝登基之前，基督教已被人们所广泛接受。故选A。