A B C Intersect
March April May June November December April May June July March December March April March
April


Code:
// Intersect
let
    Source = Excel.CurrentWorkbook(){[Name="Table4"]}[Content],
    TFC = Table.AddColumn(Source, "TFC", each Table.FromColumns({Text.Split([A]," "), Text.Split([B]," "), Text.Split([C]," ")})),
    TSC = Table.SelectColumns(TFC,{"TFC"}),
    Exp = Table.ExpandTableColumn(TSC, "TFC", {"Column1", "Column2", "Column3"}, Table.ColumnNames(Source)),
    LI = List.Intersect({Exp[A],Exp[B],Exp[C]})
in
    LI