單項(xiàng)選擇題

PSTN,PLMN,DDN分別是()

A.公眾交換電話網(wǎng),數(shù)字?jǐn)?shù)據(jù)網(wǎng),公眾陸地移動(dòng)通信網(wǎng)
B.公眾交換電話網(wǎng),公眾陸地移動(dòng)通信網(wǎng),數(shù)字?jǐn)?shù)據(jù)網(wǎng)
C.公眾長(zhǎng)途固定電話網(wǎng),數(shù)字?jǐn)?shù)據(jù)網(wǎng),公眾陸地移動(dòng)通信網(wǎng)

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