设随机变量<imgwidth="90"height="25"v:shapes="_x0000_i1078"src="http://wljy.whut.edu.cn/uploadfiles/word/xxdsb07.files/image084.png">,则<imgwidth="74"height="19"v:shapes="_x0000_i1079"src="http://wljy.whut.edu.cn/uploadfiles/word/xxdsb07.files/image086.png">服从()
①
<imgwidth="64"height="25"v:shapes="_x0000_i1080"src="http://wljy.whut.edu.cn/uploadfiles/word/xxdsb07.files/image088.png">
②
<imgwidth="48"height="21"v:shapes="_x0000_i1081"src="http://wljy.whut.edu.cn/uploadfiles/word/xxdsb07.files/image090.png">
③
<imgwidth="80"height="41"v:shapes="_x0000_i1082"src="http://wljy.whut.edu.cn/uploadfiles/word/xxdsb07.files/image092.png">
④
<imgwidth="108"height="25"v:shapes="_x0000_i1083"src="http://wljy.whut.edu.cn/uploadfiles/word/xxdsb07.files/image094.png">