11) Banded Iron Formations are interbedded iron oxides and chert that formed on the sea floor between 3.5 and 2 billion years ago because ________.

A) chert was being deposited by bacteria and iron was a common ocean deposit

B) outgassing produced both chert and iron oxide in roughly equal amounts and the oceans became

saturated with them

C) iron was using the oxygen produced by bacteria and chert was a common ocean deposit

D) iron and chert were very abundant in the early earth

E) photosynthesis had not yet started to generate oxygen so iron and chert were the deposited on the sea

floor