【单选题】
<imgwidth="434"height="21"v:shapes="图片_x0020_118"src="http://wljy.whut.edu.cn/uploadfiles/word/cyy02-60.files/image112.png">
①
<imgwidth="66"height="23"v:shapes="图片_x0020_119"src="http://wljy.whut.edu.cn/uploadfiles/word/cyy02-60.files/image113.png">
②
<imgwidth="151"height="20"v:shapes="图片_x0020_120"src="http://wljy.whut.edu.cn/uploadfiles/word/cyy02-60.files/image114.png">
③
<imgwidth="119"height="18"v:shapes="图片_x0020_121"src="http://wljy.whut.edu.cn/uploadfiles/word/cyy02-60.files/image115.png">
④
<imgwidth="118"height="18"v:shapes="图片_x0020_122"src="http://wljy.whut.edu.cn/uploadfiles/word/cyy02-60.files/image116.png">
【单选题】
<img title=无标题111.jpg alt=无标题111.jpg src=https://huaweicloudobs.ahjxjy.cn/FFCD140DADA89A325E403473DAA48141.jpg/>
①
U=<img class=jc-formula style=vertical-align: middle; src=https://huaweicloudobs.ahjxjy.cn/6A43875296E96D82DD9C7F8B49F073F6.png data-tex=U=311V\quad ,\quad \varphi ={ 30 }^{ 0 }\quad ,\quad f=50Hz\quad ,\quad T=0.02s/>
②
<img class=jc-formula style=vertical-align: middle; src=https://huaweicloudobs.ahjxjy.cn/663CC69DAF02F253B0F28D246F4B581A.png data-tex=U=220V\quad ,\quad \varphi ={ 30 }^{ 0 }\quad ,\quad f=50Hz\quad ,\quad T=0.02s/>
③
<img class=jc-formula style=vertical-align: middle; src=https://huaweicloudobs.ahjxjy.cn/DE2EF4673D0C1D771A6D98DB66C48AE1.png data-tex=U=220V\quad ,\quad \varphi ={ 30 }^{ 0 }\quad ,\quad f=314Hz\quad ,\quad T=0.02s/>
④
<img class=jc-formula style=vertical-align: middle; src=https://huaweicloudobs.ahjxjy.cn/5682E00D63ADB8357EC4F633D27AEE8C.png data-tex=U=220V\quad ,\quad \varphi ={ 30 }^{ 0 }\quad ,\quad f=50Hz\quad ,\quad T=314s/>