信息安全经历了三个发展阶段，以下____不属于这三个发展阶段。
B
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Ataskofthepostofficestaffisto_(class)mailaccordingtotheplacesitistogo
InAugust1977,asatellitetogatherdataaboutthe10millionblackholeswhicharethoughttobeintheMilkyWay.
Mrs.Weinsteinbravelyandpersistentlyusedeveryskillandpowershehadtoherattackertosimplytakehercarandnotherlife.
Theplantsneedsandwitha___(deep)ofatleast10to15cmtogrow.
两个同方向、同频率、同相位的简谐振动，振幅均为A.则它们合振动的振幅为A'=____________.