A.20%~30% B.30%~40% C.50%~60% D.70%~80%
A.將標(biāo)準(zhǔn)信號(hào)轉(zhuǎn)換成電信號(hào) B.將電信號(hào)轉(zhuǎn)換成標(biāo)準(zhǔn)信號(hào) C.將電信號(hào)轉(zhuǎn)換成物理量 D.將標(biāo)準(zhǔn)信號(hào)轉(zhuǎn)換成物理量