Which sentence is the hook in this introductory paragraph?

For the first time in decades, Baby Boomers have been outnumbered by another group--the Millennials. Baby Boomers, who were born in the '40s and '50s, are nearing or are in their elder years. Millennials, born in the twenty years leading to 2000, are now young adults. Now that they are in the majority, there are many areas where the Millennials may impact our society and priorities.     

  A. Baby Boomers, who were born in the '40s and '50s, are nearing or are in their elder years.
  B. Millennials, born in the twenty years leading to 2000, are now young adults.  
C. For the first time in decades, Baby Boomers have been outnumbered by another group--the Millennials.  
D. Now that they are in the majority, there are many areas where the Millennials may impact our society and priorities.