钢结构设计中钢材的设计强度为（）。 A: 强度标准值<img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202003/48ea082bb6914c69b614f526e5704b90.jpg"> B: 钢材屈服点<img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202003/bcb79dd9534b45bcafcee365d857a702.jpg"> C: 强度极限值<img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202003/8a5c1278c9ff4626a2e323359613a883.jpg"> D: 钢材的强度标准值除以抗力分项系数<img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202003/e6e73171d0d54a5394d3a148bc87792f.jpg">

如图所示电路的逻辑表达式F=（ ）。<img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/8655693a417e4e43a32e0732ed533c96.png" /> A: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/beda73211aea49f082d9137fd4eb0526.png" /> B: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/7388c99ee0824f20bcf85893934a2f6a.png" /> C: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/9a5c81e78b344c79a9389e932a7f55ce.png" /> D: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201909/82193a9a030243728012b02e15718987.png" />

某人举步上楼梯，每步跨1个台阶或2个台阶，设上n个台阶的不同方式数为<img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202010/62999550ec1547439283cd9872427fdc.png" />，则( ). A: 初始条件为<img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202010/e5083263b09044c1b6e95baed3ef628c.png" />=1，<img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202010/07aa95ceccda433f8e9432a186fae005.png" />= 2, 递归关系为<img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202010/ad0a958e510040be8f4253d0526d7ce5.png" />(n≥3). B: 初始条件为<img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202010/d5cc33a9d0714d3fbba386ccff5f8aaa.png" />=1，<img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202010/34a42e4a62ea448db919ffa607f5de44.png" />= 1, 递归关系为<img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202010/c3dc9b741afa4ae68983bc1d5db5e065.png" />(n≥3). C: 初始条件为<img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202010/405917811f9845e1915af00c9fa30c79.png" />=1，<img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202010/ccd3e7a79651413b8cd22dbf5cd05ac8.png" />=1, 递归关系为<img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202010/0acc9967cdab4f31a918b5fc8fe38608.png" />(n≥3). D: 初始条件为<img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202010/245baeee86b943e4bd7f1c39803b142c.png" />=1，<img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202010/a06359868bb1457e81ab7e102d212630.png" />= 2, 递归关系为<img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202010/0aee376a7bfa44da9f431ecb21e6c787.png" />(n≥3).

读装配图中零件10，下列哪个图是正确的 （ ）<img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201912/3e06ba277c804a0184232a92dc4daae8.png"/> A: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201912/f552fe75449e4a54ac92d376ccb56c4d.png"/> B: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201912/ceee8794adba4c09a22636cc1400760a.png"/> C: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201912/de760892beba4aa0b43f5ad85fa1a8e3.png"/> D: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201912/bd80973d489b4003904efdee208828b2.png"/> E: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/201912/3206dcc5d56c4536b359f5b66ae1fe03.png"/>

设A=<img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202002/bc546fc03fdb4ba3b7e6b144b6371d7f.png" />，B=Р(Р(A)) 下列（ ）表达式不成立。 A: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202002/6e615703da60435893f9e9a9273e12e5.png" /> B: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202002/64c831067d054e71a6c76f43849d450d.png" /> C: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202002/72023a5250e44c12b98923044194f13d.png" /> D: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202002/c48e039a739c4502830eee7ae0ac1678.png" />