Explanation

People in 20s - 10% read newspaper
People in 30s - 50% read newspaper

You might expect that since the younger generation is not reading the paper much, after some years, the % of people reading the paper will decrease. But the publishers claim that after some years, the % of people reading the paper will stay the same. How can you strengthen it?

What I think will strengthen it: People start reading the paper as they get older or something similar Option (C) tells you that proportion of people reading the paper in their 20s has always been low. Hence, people who are right now in their 30s were also not reading the paper much when they were in their 20s. This means that they start reading the paper at a later age. This strengthens the publishers' claim.

B, D, and E are out of scope and needn't be considered at all.

As for (A), what we are interested in is the % of paper readers within each age bracket. Whether people in their 20s are more or people in their 30s are more doesn't matter. We need to keep the % of people reading the paper the same.

Answer: C