Looking at options trading activity among components of the S&P 500 index, there is noteworthy activity today in Western Digital Corp (WDC), where a total volume of 25,970 contracts has been traded thus far today, a contract volume which is representative of approximately 2.6 million underlying shares (given that every 1 contract represents 100 underlying shares). That number works out to 43.9% of WDC's average daily trading volume over the past month, of 5.9 million shares..