Answer:
The white matter fibers are the main component of the brain. Three different types of white matter fiber are :
Commissural fibers:
This fiber is important for the connection of the corresponding left hemisphere and right hemisphere of the brain.
Projection fibers:
These fibers helps in the connection of the brain stem and the spinal cord with the cerebral cortex.
Association fibers:
These fibers are associated with the connection of the brain regions within the same hemisphere of the brain.
There are often not more than one or two independent variables tested in an experiment, otherwise it is difficult to determine the influence of each upon the final results. There may be several dependent variables, because manipulating the independent variable can influence many different things.
The answer is : randomization was not used in sample selection. The major difference between experimental and quasi-experimental designs is lack of randomization in sampling selection.
I'm thinking it might be fossil evidence. Hope it helps!
