×
单选题
Which of the following is true about secondary surveillance radar and primary radar?
A
Secondary surveillance radar uses transponders on aircraft, while primary radar uses signals reflected off objects
B
Secondary surveillance radar uses signals reflected off objects, while primary radar uses transponders on aircraft
C
Secondary surveillance radar and primary radar both use transponders on aircraft
D
Secondary surveillance radar and primary radar both use signals reflected off objects
答案解析
正确答案：A
