CREATE TABLE #Temp([File] INT, Main INT, Sub CHAR(2), [Text] VARCHAR(20));
INSERT INTO #Temp   ([File], Main, Sub, [Text])
VALUES  (1, 1, 'A.', 'hello'),
        (1, 1, 'B.', 'SQL'),
        (5, 1, 'A.', 'central'),
        (5, 1, 'B.', '.com');

SELECT 
  [File]
 ,Main
 ,[A.] = MAX(CASE WHEN Sub = 'A.' THEN [Text] END)
 ,[B.] = MAX(CASE WHEN Sub = 'B.' THEN [Text] END)
FROM #Temp
GROUP BY [File], Main;

DROP TABLE #Temp;