The Foreign Institutional Investors (FIIs) were net buyers to the tune of Rs 779.70 crore in the futures & option segment on Thursday.According to data released by the NSE, FIIs were net buyers of index futures to the tune of Rs 837.17 crore and they bought index options worth Rs 182.42 crore. They were net sellers of stock futures to the tune of Rs 236.45 crore and they sold stock options worth Rs 3.44 crore.As per data available on the Sebi website - FIIs were net sellers of stocks worth Rs 419.40 crore in the cash market on Wednesday. Mutual funds were net sellers of shares worth Rs 131.47 crore on the same day.