Some trace metals such as molybdenum and rhenium are soluble in oxygenated water.These rare metals first appeared in sedimentary rocks on Earth 2.5 billion years ago, where previously they occurred as chemical compounds in minerals.The appearance of these metals at this time indicates that
A) cyanobacteria used all available oxygen until 2.5 billion years ago.
B) meteorites from Mars carried oxygen to Earth.
C) comets brought oxygen to Earth.
D) there was no life on Earth until 2.5 billion years ago.
E) there was no atmospheric oxygen on Earth until 2.5 billion years ago.

Question

Quizplus · Accepted Answer

The appearance of these trace metals in sedimentary rocks 2.5 billion years ago indicates that atmospheric oxygen was not present on Earth before this time. These metals became soluble in water when atmospheric oxygen levels increased, likely as a result of the evolution of oxygen-producing cyanobacteria. The other answer choices are not supported by the evidence presented.

Some Trace Metals Such as Molybdenum and Rhenium Are Soluble