How can homologous structures in the forelimbs of these four organisms be used as evidence that suggests that life changes over time

It can show that they came from a common ancestor

They are evidence that the same bone structures can serve different functions in different species.

Currently, as of february 2016, an american traveling in france would be by the exchange rate. the weakness of the euro and the strength of the us dollar means that items in france cost less to an american than they otherwise would. of course, if this trend reverses and the us dollar weakens and the euro strengthens, such as was happening in early 2008, an american traveling in france would have an adverse experience because items would cost relatively more.