下列逻辑等式哪些是正确的。（） A: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202008/fb32e6d108fa4b70813a106236163c2e.png"> B: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202008/1b961d6609ad4ba1aba46badb48e054a.png"> C: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202008/b261757ec7464a438be461f017ef58c1.png"> D: A+AB=A

质点的运动学方程为x=3t, y=4t2,它在t时刻的速度矢量为 A: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202008/66e1eb9ddd424b6b8d87c9075674e17f.png"> B: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202008/9c02e87e76e142df945fb066bd6683bf.png"> C: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202008/226f38e5f86b432386fd54045299c691.png"> D: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202008/2d5ac12518a74ef78acfcc804baf219e.png">

下列函数既可用初值定理求其初值又可用终值定理求其终值的为（ ）。 A: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202008/c0d0aae9fb9a481f896ed34e749cf1cf.png"> B: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202008/8d9a5855881246e99f2f8f59ae86777e.png"> C: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202008/a567ca44e62e4194a9c152228c6c78b4.png"> D: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202008/da03b0863958465ebd3f1c53a4d252b5.png">

恒温热源温度为 T1 恒温冷源温度为 T2 ，环境温度为 T0 ，热源提供热量 Q1 中的有效能（ ） A: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202008/589db50a3273486492fd485153c10b69.png" /> B: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202008/5213b3f87eb1445ba9fff0e013545823.png" /> C: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202008/10bb86460c254dccbef1dc37b789224a.png" /> D: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202008/d12ce28fefac4fb1b94d2915f0942cc2.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).