a) A tool for fortunetelling, tarot card were believed to be introduced to Europe by Gypsys in the fifteenth century.
b) A tool for fortunetelling, tarot card are believed to have been introduced to Europe by Gypsys in the fifteenth century.
我選B,請教各位意見
關於現在完成式的使用,是看句意嗎? 還是有什麼辨別的方法 ?