Stock indexes on Friday dived to their lowest level in more than six months. The Nasdaq clanged 3.5% lower for a four-day losing streak that had to waken even the most stubborn bull. The S&P 500 and the Dow Jones industrial average shed 3.2% and 3.1%, respectively. The IBD 50 slid 3.5% as all 50 stocks fell. Volume rose on both major exchanges. Friday was an options expiration day, which tends to boost volume.