Traits controlled by genes can only be acted upon natural selection because they have to helpful to the survival of that organism.
The two serous membranes of pericardium are :visceral pericardium,parietal pericardium.
CONSTRUCTION OF HYPOTHESIS is missing from the experiment. The correct option is B.
A scientific hypothesis is a foundation that must be well laid in any scientific experimental research. A research hypothesis refers to statements made by a researcher which defines his speculations on the outcomes of the research, it is an educated guess that is based on prior knowledge and observations.
It would be B. Less force is needed to move up the ramp