Which of the following is NOT on

Which of the following is NOT one of the types of changes in word-meaning?（ ）
A、Extension
B、Degradation
C、Elevation
D、Reduction
【正确答案】：D
【题目解析】：词义变化的类型有四类：扩大（Extension）、缩小（Narrowing）、升格（Elevation）和降格（Degradation）