单项选择题

The passage is chiefly concerned with

A. offering an explanation of the process that causes a phenomenon, and a counter-explanation
B. demonstrating how two processes act in symbiotic coordination in causing a phenomenon
C. establishing how one process causes a phenomenon which is resisted by a second process
D. explaining two separate processes which cause a mostly identical phenomenon
E. outlining the essential differences between two distinct phenomenon that issue from a single cause