expiry

The option expired worthless when the price failed to reach the strike by the expiry date.当价格在到期日未能达到行权价时，该期权到期归零。

Shorter expiry options offer less time for a move but are cheaper; longer expiries give more room but cost more premium.较短期限的期权留给价格变动的时间较少但更便宜；较长期限的期权提供更多空间但权利金更高。