解:过O作OF⊥AB,交AB于点F,
又AE=3,BE=6,
∴AF=BF=
AB=1 2
(AE+BE)=4.5,1 2
∴EF=AF-AE=4.5-3=1.5,
由相交弦定理得到AE?BE=DE?EC,
∵DE=2,AE=3,BE=6,
∴EC=
=9,AE?BE DE
∴圆的直径DC=DE+EC=2+9=11,半径OD=5.5,
∴OE=OD-DE=5.5-2=3.5,
∵CP为圆O的切线,∴∠ECP=90°,
∴∠EFO=∠ECP=90°,且∠FEO=∠CEP,
∴△EFO∽△ECP,
∴
=EF EC
=EO EP
,即EO EB+BP
=1.5 9
,3.5 PB+6
解得:PB=15.
故选C