A.100ms B.200ms C.500ms D.1000ms
A.1至3 B.1至4 C.2至3 D.2至4
A.28+40log(S/λ) B.22+20log(d/λ)-(Gt+Gr) C.22+20log(d/λ) D.28+40log(S/λ)-(Gt+Gr)