user: Question: who is the incumbent where the candidates is William V. Chappell, Jr. (D) Unopposed?
Columns: ['District', 'Incumbent', 'Party', 'First elected', 'Result', 'Candidates']
Types: ['text', 'text', 'text', 'real', 'text', 'text']
Sample row: ['Florida 1', 'Robert L. F. Sikes', 'Democratic', 1940.0, 'Re-elected', 'Robert L. F. Sikes (D) Unopposed']
SQL:

assistant: SELECT "Incumbent" FROM "Table" WHERE "Candidates" = 'William V. Chappell, Jr. (D) Unopposed';