Final answer:
Without specific data, it is difficult to accurately identify which of the four countries has a coastline free of pollution. However, the environmental standards in high-income countries are generally stricter, suggesting better management of coastal pollution.
Step-by-step explanation:
When considering which of these countries appears to be free of coastal pollution, we should take into account the general environmental practices and standards of high-income versus middle- and low-income countries. High-income countries tend to have strict environmental standards and are more likely to invest in infrastructures like sewage treatment plants and technologies that reduce pollution. However, without specific data on coastal pollution for Egypt, Turkey, Saudi Arabia, and Tunisia, it's challenging to determine which country is free of coastal pollution. Such data would typically be gathered from environmental reports and studies on coastal ecosystems. In this context, it may be more relevant to look at how affluent the country is and its investment into environmental management systems, although this does not guarantee the absence of pollution.