主题：Call/Put option & Strike Price -- 罗格

任何人可以卖（write)options。电脑游戏逼你还钱的话，你肯定卖来着。假如只买的话，你不需要在任何时候还钱，最多把本儿丢光！

当你卖option的话，你手里得有一些钱或者股票。Depending on the margin rate, you don't need the full amount required to cover the whole thing, just a portion of it. Say stock A is at $10 a share now, you decided to write a July 1st 12.50 call for $3. The buyer buys the RIGHT to buy this stock @ 12.50 a share from you any time before and on July 1st. If the thing took off and went to $20 a share in April, technically the buyer can demand to buy the stock from you at the stricking price. If you have the amount of stock required in your account, you don't have to worry a thing. But if you are writing options naked - without underlying stocks - then you need to have enough money in your account to buy those stocks to cover your option. When the stock prices go up, you need more and more money.

It's simpler with Puts. You just need to have the money when people decided to sell you the stock.

据统计 30% Option到期时一文不值。(not over 50%, got my number wrong)