书中用这句话来解释当卖空股票时，借出股票的一方并没有什么成本：
In the absence of dividends, whether you receive physical possession today or at time T is irrelevant: In either case you own the stock, and at time T it will be exactly as if you had owned the stock the whole time.
Suppose that someone secretly removed shares of stock from your safe and returned them 1 year later.
From a purely financial point of view you would never notice the stock to be missing.
而我的问题是，如果我拥有一个股票，借给别人一年，如果我确定这一年之中我不会要卖出它，自然是可以认为没有成本；但如果我中途想卖出，却因为借给了别人无法卖出，不就有成本了吗？
换句话说，持有股票的好处，难道不能理解为，可以在需要把它变现成无风险资产时可以马上这样做吗？

求各位解答，感谢不尽！