【题目】The custom________the 8th century when people knew little about the earth where they lived.
A.dates back to
B.is dated to
C.is dated from
D.dates to

【答案】A
【解析】date back to/date from表示“始于；追溯到”，不用被动语态，常用一般现在时态。本句意为“这种习俗始于八世纪，当时人们对于他们所居住的地球并不了解。”