How to return dropdown menu to the default option based upon another menu?

如何返回到另一个菜单的下拉菜单的默认选项？

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Corporate equity has characteristics of options, and stock is in essence a call option based on corporate value.

公司的权益资本具有期权的特征，公司的股票实质上是基于公司价值的看涨期权。

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Mining rights of coal resources can be regarded as a multi-stage compounding real call option based on the option theory.

煤炭资源采矿权可以被认为是一个多期多阶段的复合看涨实物期权。

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He is replacing it with a plan that would provide a combined land- and sea-based capability more quickly, focused on shorter range missiles Iran could use to threaten Europe, with the option of expanding later to cover longer range missiles if necessary.

VOA: standard.2009.10.23

He was able to explain the difference between various models and helped me pick the best option based on my riding style and experience.

ENGADGET: This is the Modem World: Fear and loathing in the local bike shop

So, here's a perfectly good wireless HDMI option based on a standard that everyone and their grandmother has already adapted too -- too bad there's not a laundry list of companies already signed on to integrate it.

ENGADGET: Celeno and Cavium team up for WiFi-based wireless HDMI solution

That option is based on the New York guardianship standards.

FORBES: Amanda Bynes' Comeback Could Begin With A Guardianship