Critical Reasoning

Sociologists often refer to certain age groups in this country in terms of the generation to which they belong. All of those born before 1940 are generally considered the Pre-War Generation. The Baby Boomer Generation includes those people born from 1941 to 1960, during or after World War II. Those born from 1961 to 1975, are referred to as Generation X, most noted for their supposed disillusionment with the attitudes about career ambition and money-making held dear, according to sociologists, by the Baby Boomers. Generation Y refers to all those born in 1975 or later. However, a new name, Generation D, or Digital, has been coined very recently. Generation D is often defined by the fact that its members grew up with, and integrate, computer and Internet technology into every aspect of their lives.

According to the information provided above, which of the following must be true?
a)No members of Generation X are members of Generation D.
b)All members of Generation X disagree with the attitudes of Baby Boomers about career ambition.
c)All members of Generation D are also members of another generation.
d)No person can be a member of more than one generation.
e)All members of Generation Y are also members of another generation.

i just cant take the OA provided in the question..this is too much..can someone help!
OA is C