Final answer:
The inability to identify the conclusive location of the root for the three main branches of the tree of life is due to different sets of genes supporting different locations for the placement of the root.
Step-by-step explanation:
The explanation that best summarizes why scientists have been unable to identify the conclusive location of the root for the three main branches of the tree of life is C) There is plenty of information on nucleotide sequences but different sets of genes support different locations for the placement of the root.
Scientists have analyzed nucleotide sequences to determine the relationships among organisms. However, different sets of genes provide conflicting information, supporting different locations for the root of the tree of life. This makes it challenging to identify the definitive location of the root.