Rawquery() can only read few first rows?

I tried to use custom ResourceCursorAdaptor to provide data for my ListView. Whenever I read data from my custom database, the cursor would only have few rows.

@Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setRetainInstance(true);
        QuizDBOpener opener = QuizDBOpener.getInstance(this.getActivity());
        SQLiteDatabase db = opener.getReadableDatabase();
        Cursor c = db.rawQuery("SELECT quizNum as _id, quizTitle, quizDesc FROM quiz", null);
        QuizListAdapter qlAdapter = new QuizListAdapter(getActivity(), c);
        setListAdapter(qlAdapter);
    }

However, I put this line. Somehow the code work. But obviously this is not what I want.

SystemClock.sleep(500);

So, how should I deal with rawQuery()? Where am I doing wrong?