The word their in the last paragraph refers to .

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions.
The generation gap that was so in evidence during the 60s has resurfaced, but a 2009 study showed that it was not the disruptive force. The Pew Research Center study found that 79% of Americans see major differences between younger and older adults in the way they look at the world. In 1969, a Gallup Poll found that a smaller percentage, 74%, perceived major differences.
Today, however, although more Americans see generational differences, most do not see them as divisive. That is partly because of the areas of difference. The top areas of disagreement between young and old people, according to the Pew Research Study, are the use of technology and taste in music. Grandparents are likely to have observed these differences in their grandchildren who are tweens, teens, and young adults.
If large differences between the generations exist, why don't they spawn conflict? The answer is twofold.
First, the two largest areas of difference - technology and music - are less emotionally charged than political issues. The older generation is likely to be proud of the younger generation's prowess in technology rather than to view it as a problem. As for the musical differences, each generation wants its own style of music, and the older generation generally can relate to that desire. Second, in the other areas of difference, the younger generation tends to regard the older eneration as superior to their own generation – clearly a difference from the 1960s with its rallying cry of "Don't trust anyone over thirty!". According to the Pew study, all generations regard older mericans as superior in moral values, work ethics and respect for others.