x1,x2,…,xn是从正态总体N(μ,σ2)中抽取的样本,若σ2已知,,则μ的置信水平为0.95的置信区间是()
A <img src="https://www.beizhujiaoyu.com/uploads/202208/161223783873921.png" width="240" height="40" /> B <img src="https://www.beizhujiaoyu.com/uploads/202208/161223785142911.png" width="230" height="40" /> C <img src="https://www.beizhujiaoyu.com/uploads/202208/161223785663621.png" width="233" height="40" /> D <img src="https://www.beizhujiaoyu.com/uploads/202208/16122378601811.png" width="233" height="39" />