【单选题】
下列命题联结词集合中，是最小联结词组的是（ ）
①
{┐，<imgwidth="20"height="11"style="-aw-left-pos:0pt;-aw-rel-hpos:character;-aw-rel-vpos:line;-aw-top-pos:0pt;-aw-wrap-type:inline"src="../uploadfiles/word/lsss001.files/image077.png">}
②
{┐，∨，∧}
③
{┐，∧}
④
{∧，→}
【单选题】
<imgdata-url="doc/a@A5D73AD1B9876D3B1284C39D684E7736.png"data-preview_url_ueditor="doc/a@A5D73AD1B9876D3B1284C39D684E7736.png"src="http://121.251.253.213/doc/a@A5D73AD1B9876D3B1284C39D684E7736.png/download?time=635997619599470663&token=543BDEAD2F9916CA87B05DCF8C27A0AA&filename=png"/>
①
PA=B
②
AP=B
③
PB=A
④
BP=A