The correct answer is: A. 1.3 Billion years
Blue-green algae are the oldest fossils found on Earth. They were found in limestones with the age almost as old as 1.3 billion years.
Blue-green algae are a type of bacteria that can photosynthesize. They are the oldest known photosynthetic organisms and are thought to have played a major role in the development of the Earth’s atmosphere.
Limestone is a type of sedimentary rock that is formed from the accumulation of calcium carbonate. It is often found in marine environments and can be used to date fossils.
The age of a fossil can be determined by a variety of methods, including radiometric dating and stratigraphy. Radiometric dating is a technique that uses the decay of radioactive elements to determine the age of a rock or fossil. Stratigraphy is the study of the layers of rock and their relative ages.
The fossils of blue-green algae found in limestones with the age almost as old as 1.3 billion years provide evidence that these organisms were present on Earth at a very early stage in its history. This finding suggests that blue-green algae may have played a role in the development of the Earth’s atmosphere and the evolution of life on Earth.
The other options are incorrect because they are not as old as 1.3 billion years.