下列关于极值命题中正确的是（） A: 若<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202007/66e36e20da3f43e9bbd9ce0f42dcbe28.png">，则<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202007/9d60dd3351b54052b4f4afe27423a0e7.png">必是<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202007/53f1ecb5821b44f1a56bbc836e49d9b7.png">的极值点 B: 若<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202007/0a40a2ad34e649e3b999f776e8fe1919.png">，则<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202007/9d60dd3351b54052b4f4afe27423a0e7.png">必是<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202007/53f1ecb5821b44f1a56bbc836e49d9b7.png">的极值点 C: 极大值一定大于极小值 D: 若<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202007/31b1a07ab57347febde3751859364dfb.png">存在且<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202007/9d60dd3351b54052b4f4afe27423a0e7.png">是极值点，则必有<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202007/66e36e20da3f43e9bbd9ce0f42dcbe28.png">

图示刚架,结点A承受力偶作用，EI=常数。用力矩分配法求得AB杆B端的弯矩是：（）<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202007/7f7f4973567d4fe1bba22dcfda90576b.png"> A: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202007/924668c9b6164abf9ce5f8408ce20881.png"> B: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202007/7138e815e3484afc811e172c08c9c5ed.png"> C: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202007/e69f09485ad04e40851c731afb2381a2.png"> D: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202007/33f68a0494134087b303dd17cfaca7b1.png">

计算机控制系统中，若被控对象传递函数为<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202007/449150d9457a43b98c14899c6ffa5b27.png" >，设采样周期T=1s，则其广义被控对象的脉冲传递函数为（）。 A: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202007/eda76ecd0c754547a9d40ec652dd6389.png" > B: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202007/950619299fc9457cab633a4abf11df94.png" > C: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202007/f1b3a243951e47f0965e825c0ef3d0d8.png" > D: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202007/817b81563181439e8e54ea1de38e039f.png" >

有一段距离，其观测值及其中误差为<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202007/955e74e32ce34326bdef41ac92072428.png" >，这个观测值的真误差的实际可能范围是（）。 A: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202007/bfa41dfe10ae4573a7330618be9a2d68.png" > B: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202007/678e81221188413e98d0eb203cc923d1.png" > C: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202007/c105a1d6bdc84db494d58aebe03aded0.png" > D: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202007/949892fc01a74c8188fdcf6e1aa59ad0.png" >

有6本中文书和4本外文书，任意往书架摆放，则4本外文书放在一起的概率是(). A: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202007/a134393932b84674ba322b5f9497f589.png" > B: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202007/ca652e863e0d486b9d28fa71d8427dbf.png" > C: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202007/50aacfa724d4470ca1fc065813e47e39.png" > D: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202007/f681e33f0f9849a0a444a4ecfc9db061.png" >