Long term trends over geological history in speciation and extinction rates can be partially explained by
a. natural selection in small populations
b. over harvesting by humans
c. plate tectonics and continental drift
d. short term changes in present day environment

The correct answer is option C, that is, plate tectonics and continental drift.

Explanation:

The rate of extinction and speciation of organisms relies upon various factors, of which one is the spatial distribution of the species. The continental drift and tectonic movements make a small group of a specific species to distinguish or move away from the mainland that in turn results in speciation.  

Some of the species that cannot cope and are not able to survive because of the lack of food and breeding may become extinct during the process. Thus, the correct answer is option C.  

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b brown mice / white sand dunes