问题
单项选择题
Radar is used to extend the ______ of man's senses for observing his environment, especially the sense of vision.
A．validity
B．liability
C．capacity
D．intensity
答案
参考答案：D
解析： validity“有效性，合法性”；liability“责任，负债”；capacity“容量，地位”；intensity“强烈，强度”。答案是D。