The conclusion that can be made by the reader is:
A. Grandparents have a significant influence on their grandchildren's emotional well-being.
The sentence that best supports this answer is:
C. The tales they tell can be stabilizing forces in the day-to-day bustle and high excitement of the very young and, by the nature of a grandparent's role, suggest channels for positive values. (paragraph 2)
This sentence highlights how the stories and role of grandparents contribute to emotional stability and the instilling of positive values in their grandchildren, which supports the idea of their significant influence on emotional well-being.