Final answer:
Vaillant's "keepers of meaning" describes adults in midlife, typically ranging from the age of 40s to mid-60s, focusing on generativity and societal contribution.
Step-by-step explanation:
Vaillant's concept of "keepers of meaning" refers to adults in midlife, typically those who are in their middle years and are often seen as being in a phase of life where they contribute to the development of others and society as a whole. This period, which can be defined as ranging from one's 40s to the mid-60s, is marked by a focus on generativity versus stagnation. Individuals at this stage might engage in activities such as volunteering, mentoring, or raising children, all ways of contributing and keeping the culture and societal values alive for future generations. Therefore, the correct answer is A. Adults in midlife.