单项选择题

TEXT D
What has the telephone done to us, or for us, in the hundred years of its existence A few effects suggest themselves at once. It has saved lives by getting rapid word of illness, injury, or fire from remote places. By joining will the elevator to make possible the multi-story residence, e or office building, it has made possible— for better or worse— the modern city. By bringing about a great leap in the speed and ease with which in formation moves from place to place, it has greatly accelerated the rate of scientific and technological changes and growth in industry. Beyond doubt it has seriously weakened if not killed the ancient art of letter writing. It has made living alone possible for persons with normal social in pulses; by so doing, it has played a role in one of the greatest social changes of this century, the breakup of the multi-generational household. It has made the war chillingly more efficient than formerly. Perhaps, though not provably, it has prevented wars that might have arisen out of international misunderstanding caused by written communication. or per haps—again not provably—by magnifying and extending irrational personal conflicts based on voice contact, it has caused wars. Certainly it has extended the scope of human conflicts, since it impartially disseminates the useful knowledge of scientists and the nonsense of tire ignorant, the affection of the affectionate and the malice of the malicious.
The author describes the telephone as impartial because______.