B. Alone on an island, Crusoe has many technologies for producing wealth. From a purely selfish point of view, people who refuse to trade are just hurting themselves. In other words, without property rights, the property probably wouldn't have existed in the first place. Of course, it is possible for something to be unowned. This has frequently happened.
Oceans are normally unowned, accessible to all.
Since no one owns it, people use it without regard to the effect on others. And, once you realize that people think this way, you also have an incentive to take as much as possible NOW, because the resource won't be useful very long. That is the benefit of property rights that is absent in the commons - a benefit not just for owners, but for users as well.