India's benchmark gauge of protection against stock-market swings surged by the most since May after the longest stretch of option purchases by foreigners in 21 months. The India VIX Index jumped 13 per cent to 16.4 in Mumbai, the highest close since July 9. Foreign investors bought a net $76.5 million of CNX Nifty Index options on October 14, an 11th day of purchases and the longest streak since January 2013, Bloomberg data show.