Evolutionary tree is constructed to understand the phylogeny and evolution relationship of the organism. The evolutionary tree is constructed by looking at the molecular and physiology of the different organisms.
The eukaryotes are more closely related to the archaea. Depending on the biochamical and molecular evidence is has been found that they share the common ancestor almost 2.5 billion years ago. This can also be deduced by the fossil evidence as well.
The life on the earth has evolved with 3 different lineage namely Bacteria, Eukarya, and Archaea. However the 2 are prokaryotic groups of microbes that lack membrane bound organelles and nuclei.
Recent studies suggested that these two domain, Eukarya and the Arcahea are more close than the bacteria domain. These two domains are shared the common ancestor that probably existed 2.5 billion years ago.
Thus, the correct answer is - 2.5 billion years ago.
My best guess would be c because b makes no since we as humans do not have photosynthesis and are considered living organisims, d is also wrong because the brain requires oxygen, and its not a because the brain is made of cells.
