Spraying insects with a pesticide ddt causes some pesticide resistance in insect populations. The changes that occur in the insect population are related to a pattern in genetic inheritance. Repeated spraying kills many insects; however, more frequent spraying and higher concentrations fail to kill insects. In this environment, the spaying of insects appears to act as SELECT ONE:
A. BIOLOGICAL FACTOR
B. GROWTH INHIBITOR
C. AN AGENT OF SELECTIVE PRESSURE
D. AN AGENT TO ELIMINATE OLD WEAK INSECTS