下列定义数组的语句中，正确的是 A: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201903/bce86560abbe4188b0be7d0139cabf5e.png" /> B: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201903/5e1379bc3ed248bebf017b0f99b7336c.png" /> C: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201903/48fe317cb5984864892173700f139ef7.png" /> D: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201903/ac6f09707b864ab7aeae4a4f6dc14453.png" />

信号 如图所示，求其频谱。http://image.zhihuishu.com/zhs/onlineexam/ueditor/201903/e7cf021b113341e4bb5ee98d7d12e0f2.png

C语言程序经过编译、连接后生成的可执行文件的扩展名是 A: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201903/c27145d4741c4f0f96beadcf86ba18ab.png" /> B: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201903/9f40e97bb87546d393b24501e95aae0b.png" /> C: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201903/c7e1150c6e0d4974ae48ddeb44c71cab.png" /> D: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201903/eb4766c9737948f5b631dd909d2b94e4.png" />

某离散时间系统的系统框图如图所示，其中x表示输入信号，Y表示输出信号，系统的差分方程可以表示为？<img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201903/f17b1754961a482eb540b5229ed1d3b7.png" /> A: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201903/0769d057673d4151b1f0b41af2ffe512.png" /> B: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201903/3538ab9355d34bdb854faaddbd64abd6.png" /> C: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201903/62652baf39794e328f736a5e1dc4a701.png" /> D: <img src="http://image.zhihuishu.com/zhs/onlineexam/ueditor/201904/90ff953c2cb044b8a0662afaf143d417.png" />

http://image.zhihuishu.com/zhs/onlineexam/ueditor/201903/f1b80e3562034f6394f9bb8fbbafbbf1.png