It is heat, convection cells in the asthenosphere cause the movement of the crust.
NACL is the correct answer
It is c.a decrease of gravity!!
When a lineage splits into multiple line of descents, then, it leads to speciation. It is a process by which a single population evolves into different species. The process of speciation leads to the development of two or more species as the lineages are splitted. These two evolved species are genetically independent.
Hence, the blank can be filled with 'speciation'.
