It was not simply a practical matter, but a fundamental question

It was not simply a practical matter, but a fundamental question of（ ）.
A、discipline
B、theory
C、principle
D、nature
【正确答案】：C
【题目解析】：本题考查名词辨析。discipline：学科；theory：理论；principle：原则；nature：自然。句意：那不仅仅是个实际问题，更是一个根本性的原则问题。故C选项符合题意。