【单选题】
下列命题正确的是()
①
{l,2}<imgwidth="15"height="15"src="../uploadfiles/word/lsss001.files/image011.png">{{1,2},{l,2,3},1}
②
{1,2}<imgwidth="15"height="15"src="../uploadfiles/word/lsss001.files/image011.png">{1,{l,2},{l,2,3},2}
③
{1,2}<imgwidth="15"height="15"src="../uploadfiles/word/lsss001.files/image011.png">{{1},{2},{1,2}}
④
{1,2}∈{1,2,{2},{l,2,3}}