Question 25 is based on the passage you have just heard.

听力原文    

        Maybe you carry the most powerful passport in the world, or perhaps the rarest passport. Whatever the case, your passport will likely be one of four colors: red, blue, green or black, although there are slight variations. Switzerland’s passport is dark red, for example, (22) [while most European countries prefer a shade of red that’s almost brown.] There are no official rules regarding passport colors, (23) [but countries follow a certain set of norms when designing them.] The International Civil Aviation Organization, which works to define the principles of air travel, suggests that countries use a suitable type, size and style for official documents like passports. There are also a few compulsory aspects of passports. They must be made from a material that bends. They should be able to be read by a machine at temperatures ranging from 10℃ to 50℃ and conditions where the air can be extremely dry or moist. Despite these existing recommendations, there is nothing regarding the cover color. Why? (24) [Simply put, countries stick to darker and more conservative colors because they appear more official] and they can also hide dirt and wear. While there’s little innovation when it comes to passport cover color, the same cannot be said for the pages. (25) [The passports of many countries contain images of their well-known geographical features and wildlife, which also function as security features as some are only visible under a special light.]

25. What is one special function of the images inside many passports?（很多护照里面的图像有什么特殊功能？）

解析：D。录音中提到，许多国家的护照内页都有其广为人知的地理特征和野生动物的图像，这些图像也起到了安全功能，因为有些图像只有在特殊光线下才能显示出来。D项与此相符，其中的security为原词复现，故D项正确。

错项排除：A项和B项在录音中未提及，故排除。C项利用录音最后出现的visible一词作干扰，但录音说的是有些图像只有在特殊光线下才能显示出来，是通过图像的可视性达到安全的目的，因此可视性并非图像的功能而是实现安全功能的手段，故C项错误。