【单选题】

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