______ is one of the factors that tend to promote social change.

参考解析：

细节理解题。根据第一段前三句“Social change is more likely to occur in societies where there is a mixture of different kinds of people than in societies where people are similar in many ways. The simple reason for this is that there are more different ways of looking at things present in the first kind of society. There are more ideas, more disagreements in interest, and more groups and organizations with different beliefs.”可知，在有更多的想法，更多的利益分歧，更多的团体和组织有不同的信仰的社会里，更容易发生社会变革，所以A项错误，所以D项正确；根据第二段可知，在一个社会中，物质方面的社会变革也可能更频繁、更容易发生。例如，在技术上、在晚年学到的东西、在社会的不那么基本和不那么感性的方面等，所以B项和C项错误。故选D。