invalid column exception

Hi,
I have the following query

"SELECT Test_Question.Question_ID, Test_Question.Grade_Number as GNum, Test_Question.Question_Number as QNum, Question.Question_Text as QText , Answer.Answer_Number as AnsNum, Answer.Answer_Text as AnsTxt, Answer.ID AS Ans_ID FROM Test_Question, Question, Answer WHERE Test_Question.Active=1 AND Test_Question.Question_ID = Question.ID AND Test_Question.Deleted=0 and Test_Question.Test_Detail_ID ="+ currPTestId +" AND Question.ID = Answer.Question_ID GROUP BY Test_Question.Question_ID ORDER BY Test_Question.Question_Number, Test_Question.Question_ID, Answer.Answer_Number";

But I get an exception column Test_Question.Grade_Number is invalid in the select list because it is not contained in either an aggregate function or the group by clause.

Could some one point out what is the problem in the above query.

thanks in advance
shailinclude that column too in the groupby list.

hth