89C51单片机访问外部数据存储器时，不起作用的信号是（ ）。
A:
B:
C:
D: ALE
A:
B:
C:
D: ALE
举一反三
- Which of the followings is a viaduct bridge? A: <img src="https://image.zhihuishu.com/zhs/teacherExam_h5/COMMONUEDITOR/202108/59165a26ff90451c870bd564d76b5c18.png" /> B: <img src="https://image.zhihuishu.com/zhs/teacherExam_h5/COMMONUEDITOR/202108/fb823138340242648983d6067fd232d0.png" />
- Which of the followings is a tied arch bridge? A: <img src="https://image.zhihuishu.com/zhs/teacherExam_h5/COMMONUEDITOR/202108/fc874d8df89249de957c02d253f7e0ff.png" /> B: <img src="https://image.zhihuishu.com/zhs/teacherExam_h5/COMMONUEDITOR/202108/7ca3186696284b4f9965df4de9075b3d.png" />
- 对200~400nm范围内的电磁辐射没有吸收的化合物是（ ） A: <img src="https://image.zhihuishu.com/zhs/teacherExam_h5/COMMONUEDITOR/202108/339ea7f3e0a4494aaebb954844cd91e5.png" /> B: <img src/><img src="https://image.zhihuishu.com/zhs/teacherExam_h5/COMMONUEDITOR/202108/f39327046f604fdda4ac0cb3774e8d95.png" /> C: <img src="https://image.zhihuishu.com/zhs/teacherExam_h5/COMMONUEDITOR/202108/dc167e1bb86e42fe963bb5144ec5ef61.png" /> D: CH2=CH-CH=CH2
- 下列哪种是已知正六边形外接圆的直径绘制六边形的方法？（） A: <img src="https://image.zhihuishu.com/zhs/teacherExam_h5/COMMONUEDITOR/202108/e70c3e886080447aa65c1d35726a83bb.png"> B: <img src="https://image.zhihuishu.com/zhs/teacherExam_h5/COMMONUEDITOR/202108/0f8c6c84762542289f395367240ae4c3.png"> C: <img src="https://image.zhihuishu.com/zhs/teacherExam_h5/COMMONUEDITOR/202108/b4f8609ee9504f4bb90ce3fcc768a356.png">
- <img src="https://image.zhihuishu.com/zhs/teacherExam_h5/COMMONUEDITOR/202104/c3b75de7a0ff4216a7c936dfa863e921.PNG" /> A: <img src="https://image.zhihuishu.com/zhs/teacherExam_h5/COMMONUEDITOR/202104/9bc090082ac447aab731646e7ce4a372.PNG" /> B: <img src="https://image.zhihuishu.com/zhs/teacherExam_h5/COMMONUEDITOR/202104/5666843a7db64c75a2ec586b2db2f35f.PNG" /> C: <img src="https://image.zhihuishu.com/zhs/teacherExam_h5/COMMONUEDITOR/202104/fd98481c51284a9db6d3c21bd7fa60ca.PNG" /> D: <img src="https://image.zhihuishu.com/zhs/teacherExam_h5/COMMONUEDITOR/202104/6f7725736cf84d439343d0c213a650e7.PNG" />