The call is "covered" because you have 100 shares of the underlying stock as collateral. Looking at Microsoft's options chain as of Dec. 23, you could sell a one-month covered call expiring on Jan ...

Specifically, 43,342,600 calls and 19,515,287 puts were traded in the last 10 sessions — the most of any stock on the list. Notably, the weekly 1/10 150-strike call was the most traded contract.