肠道中的微生物与我们的健康息息相关，一般肠道中大约有多少微生物，可培养到的大约多少种？
A:
B:
C:
D:
A:
B:
C:
D:
举一反三
- 在HTML中，表示内嵌CSS样式的标记是（ ）。 A: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202009/0f0459998c5c468d9f4da1cda1efa615.png" /> B: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202009/4defb3f96a4943559f8517f5fa1dd9b0.png" /> C: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202009/89f0de7112d641a1abb2c95a82733322.png" /> D: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202009/775faf4c538b484abd2b320e8d165e4a.png" />
- 在FeBr3存在下，下列化合物中与Br2最易反应的是 A: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202009/b390d91bdb2642eb922cda903d861e96.png"> B: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202009/10344dabb53f493c909c2bcd1f2f7764.png"> C: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202009/ec45a2a1fdd84ce0b3fd81823b9c375f.png"> D: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202009/7c99b94959254b13b21e06a97f6ba58a.png">
- HTML文档的树状结构中，（ ）标签为文档的根节点，位于结构中的最顶层。 A: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202009/5723e086f123444081427c389e4872e6.png" /> B: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202009/a217e300ab6c48f69256f71f237461f7.png" /> C: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202009/b98cb4d6a4c34f099e97086a0515df11.png" /> D: <img src="https://image.zhihuishu.com/zhs/onlineexam/ueditor/202009/530a46c2a38641bebc135da4c9598821.png" />
- 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).