21.   According to Vachon, the government has not yet given a definitive answer.

22.   But Beauman gives us no definitive answer as to how Rebecca died.

23.   But he said in a telephone interview that the data did not provide a definitive answer.

24.   But he said officials never got a definitive answer.

25.   But definitive answers may be elusive.

26.   But in the most confounding cases, researchers must rely on exhaustive psychological studies to determine suicidal motives, leaving definitive answers unknown.

27.   But it is problematical whether the study will provide definitive answers, and especially whether it will provide a clear enough idea of what the pre-Columbian ecosystem was like.

28.   But it would put his accomplishment in position to spark debate over topics that have no definitive answers.

29.   But it should not be seen as a definitive answer to the recent sharp rise in oil prices.

30.   But scientists who are trying to get a definitive answer to this question are finding that it is excruciatingly difficult and, some say, impossible.