Final answer:
The correct transition to show the relationship between the ideas in the given excerpt is 'For example.'
Step-by-step explanation:
The correct transition to show the relationship between the ideas in the given excerpt is For example. This transition is used to provide an example or illustration to support a point or argument. In the excerpt, the author is discussing the initial satisfaction of eating fast food but also the negative effects it can have on health. When using the transition 'For example,' the author could then provide a specific example of the negative effects of fast food on health, such as obesity or cardiovascular disease.