ASP.Net c# - MySQLTransaction多重插入

从我以前的问题张贴在这里(两个插入查询链接字段)，为什么下面的代码插入4个新行在'question_m'表，当我想只插入1行?此外，以下代码在"答案"表中插入16行新行，而不是4行?

下面是执行这段代码后的表的屏幕截图:

'questions_m'表- https://i.stack.imgur.com/f3DrZ.png

'answers'表- https://i.stack.imgur.com/PaTvO.png

    string connStr = ConfigurationManager.ConnectionStrings["myConnectionString"].ConnectionString;
    using (MySqlConnection conn = new MySqlConnection(connStr))
    {
        conn.Open();
        using (MySqlTransaction tr = conn.BeginTransaction())
        {
            string queryUpdateQuestions = @"INSERT INTO questions_m (module_id, author_id, approved, question, type) VALUES (@module_id, @author_id, @approved, @question, @type);
            SELECT LAST_INSERT_ID()";
            using (MySqlCommand cmdUpdateQuestions = new MySqlCommand(queryUpdateQuestions, conn, tr))
            {
                cmdUpdateQuestions.Parameters.Add("@module_id", MySqlDbType.VarChar);
                cmdUpdateQuestions.Parameters["@module_id"].Value = ddlModules.SelectedValue.ToString();
                cmdUpdateQuestions.Parameters.Add("@author_id", MySqlDbType.VarChar);
                cmdUpdateQuestions.Parameters["@author_id"].Value = Session["UserID"].ToString();
                cmdUpdateQuestions.Parameters.Add("@approved", MySqlDbType.VarChar);
                cmdUpdateQuestions.Parameters["@approved"].Value = 'N';
                cmdUpdateQuestions.Parameters.Add("@question", MySqlDbType.VarChar);
                cmdUpdateQuestions.Parameters["@question"].Value = txtQuestion.Text;
                cmdUpdateQuestions.Parameters.Add("@type", MySqlDbType.VarChar);
                cmdUpdateQuestions.Parameters["@type"].Value = ddlQuestionType.SelectedValue.ToString();
                int lastQuestionID = Convert.ToInt32(cmdUpdateQuestions.ExecuteScalar());
                ViewState["lastQuestionID"] = lastQuestionID;
            }
            string queryUpdateAnswers = @"INSERT INTO answers (question_id, answer, correct) VALUES (@question_id, @answer, @correct);
                                    SELECT LAST_INSERT_ID()";
            using (MySqlCommand cmdUpdateAnswers = new MySqlCommand(queryUpdateAnswers, conn, tr))
            {
                cmdUpdateAnswers.Parameters.Add("@answer", MySqlDbType.VarChar);
                cmdUpdateAnswers.Parameters.Add("@question_id", MySqlDbType.Int32);
                cmdUpdateAnswers.Parameters.Add("@correct", MySqlDbType.VarChar);
                int lastAnswerID = 0;
                int a = Convert.ToInt32(ddlNoOfAnswers.SelectedValue.ToString());
                for (int b = 1; b <= a; b++)
                {
                    cmdUpdateAnswers.Parameters["@answer"].Value = ((TextBox)this.FindControl("txtAnswer" + b)).Text;
                    cmdUpdateAnswers.Parameters["@question_id"].Value = Convert.ToInt32(ViewState["lastQuestionID"]);
                    if (b == 1)
                    {
                        cmdUpdateAnswers.Parameters["@correct"].Value = "Y";
                    }
                    else
                    {
                        cmdUpdateAnswers.Parameters["@correct"].Value = null;
                    }
                    lastAnswerID = Convert.ToInt32(cmdUpdateAnswers.ExecuteScalar());
                }
            }
            tr.Commit();
        }
    }