combobox syntax

Question

I am getting an error like Syntax error (comma) in query expression 'marks,chaptername='2''Electromagnetic Induction''.  

what query i should write to select from both combomarks and combochapters  and display the set of questions the particular chapters accoding to the marks selected  in c#?

private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)

        {

            checkedListBox2.Items.Clear();

            //cmbosubject.Items.Clear();

            OleDbConnection con = new OleDbConnection(@"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + Application.StartupPath + "\\easyexamdb.mdb");

            con.Open();

            str = "select * from tblmcq where marks,chaptername='" + comboBox1.Text + "''" + checkedListBox1.SelectedItem + "'";

            com = new OleDbCommand(str, con);

            OleDbDataReader reader = com.ExecuteReader();

            while (reader.Read())

            {

                checkedListBox2.Items.Add(reader["question"]); //.ToString());

            }

            con.Close();

            reader.Close();
}