Question: Who sings for UB40, Duncan Campbell or Park So-yeon?

Context paragraphs:
Ali Campbell: Alistair Ian "Ali" Campbell (born 15 February 1959) is an English singer and songwriter who was the lead singer and a founding member of the English reggae band UB40.  As part of UB40, Campbell sold over 70 million records worldwide and toured the globe for 30 years.  In 2008, Campbell left UB40 and embarked on a solo career.  In 2012, Campbell was announced as one of the three judges on the judging panel of the TV show, "New Zealand's Got Talent".  In August 2014, Campbell announced that he had reunited with former UB40 band mates Astro and Mikey to record a new album, "Silhouette", released on 6 October 2014.

ABC trial: The ABC Trial was a trial of charges under sections 1 and 2 of the Official Secrets Act 1911 trial in United Kingdom.  It took place in 1978 and is named after the three defendants: Crispin Aubrey, John Berry and Duncan Campbell.  Aubrey was a journalist for "Time Out", John Berry was a former corporal in signals intelligence (SIGINT), and Duncan Campbell was an investigative journalist.

Duncan Campbell (died 1758): Duncan Campbell was a Scots nobleman who died on 18 July 1758 as a result of wounds received in an unsuccessful frontal attack against French forces at Fort Carillon (renamed Fort Ticonderoga when the British took the fort a year later).  The legend associated with Campbell is that a number of years prior—while still living in Scotland—Campbell gave shelter to a stranger who turned out to have killed Duncan's cousin.  Faced with the conflict between betraying a guest or taking vengeance for the death of his cousin, Campbell compromised by allowing the killer to hide out in a cave.  The ghost of Campbell's cousin is claimed to have appeared to Campbell in a dream and promised to meet him again at "Ticonderoga", a place that Duncan surely had never heard of previously.  This story was published in the poem "Ticonderoga a Legend of the West Highlands" by Robert Louis Stevenson in "Scribner's Magazine" December 1887.

Duncan Campbell (UB40): Duncan Campbell (born 3 April 1958 in Birmingham) is an English musician and current lead singer of the reggae band, UB40.  He joined the band in 2008 after the departure of his brother Ali Campbell.

Campbell of Auchinbreck: The Auchinbreck of Campbell family (also spelled Auchenbreck, Achnabreac, etc., from Scots Gaelic "Ach[adh] nam Breac" meaning either Field of the Trout or Speckled Field), was founded by Duncan Campbell of Kilmichael, in Glassary, Argyllshire, Scotland.  He was the son of Duncan, first Lord Campbell of the Clan Campbell, by his second wife Margaret, daughter of Sir John Stewart of Blackhall, the illegitimate son of King Robert III of Scotland.  The family of the Lords Campbell later became Dukes of Argyll, and remain chiefs of Clan Campbell.  Duncan Campbell, as a grandson of King Robert III, received a considerable estate confirmed by royal charter dated 19 June 1452.  The family remained at their estate of Auchinbreck, from which they took their title, until 1641.  The Campbells of Auchinbreck were commissioned to provide military training and were used by the Earls of Argyll as military support.  In 1628 the then head of the family of Campbells in Auchinbreck received a baronetcy, which included a grant of North American land in Nova Scotia.

Park So-yeon (singer): Park So-yeon (born October 5, 1987), better known mononymously as Soyeon, is a South Korean singer and actress.  She is best known as the former main vocalist and member of South Korean girl group T-ara.

George Campbell of Inverneill: George Campbell was born in 1803, the first son of Duncan Campbell of Inverneill B.C.S. and his wife, Elizabeth Cooper.  He was a grandson of James Campbell (1706–1760) 3rd of Tuerechan (8th Chief of Tearlach, descended from Clan Campbell of Craignish) and nephew of Major-General Sir Archibald Campbell KB, father-in-law to Colonel Thomas Tupper Carter-Campbell of Possil and grandfather to General George Tupper Campbell Carter-Campbell CB, DSO.  He had a son and two daughters with his wife Susan "Black Beauty" Campbell of Possil (daughter of Col. Alexander Campbell of Possil).

Campbell of Craignish: The Campbells of Craignish ("Mac Dúbhghaill Creaginnis" in the Scottish Gaelic or "Gàidhlig"), form one of the oldest branches of the ancient and powerful Clan Campbell in Scotland. .  They claim descent from Dugald Campbell, the second son of Sir Archibald Gillespic Campbell (b.1130), 5th Knight of Lochawe and 20th Chief of Clan Campbell at the time.  Sir Archibald's first son, Sir Duncan Campbell, 6th Knight of Lochawe, was the founder of the principal branch of the Campbell family who today holds the title Duke of Argyll.

Labour of Love IV: Labour of Love IV is the seventeenth album and fourth covers album by UB40, released on the Virgin Records label in 2010.  It is the first UB40 album not to feature the classic line-up as longtime UB40 vocalist/guitarist Ali Campbell and keyboardist Mickey Virtue both departed the band in 2008; consequently it is the first album by the band to feature vocalist Duncan Campbell.

Duncan Campbell, 1st Lord Campbell: Duncan Campbell, 1st Lord Campbell (Classical Gaelic "Donnchadh mac Cailein", and also called Donnchadh na-Adh (English: Duncan the fortunate ) of Loch Awe, (died 1453), was a Scottish nobleman and politician.  He was an important figure in Scottish affairs in the first half of the 15th century and Justiciar of Argyll.  He was head of the Clan Campbell for 40 years.

Supporting paragraphs: Duncan Campbell (UB40) Park So-yeon (singer)
Answer: Duncan Campbell