What conclusion can be drawn from the last paragraph of the passage about researches condu

What conclusion can be drawn from the last paragraph of the passage about researches conducted concerning ageism？

A．The author is trying to make something clear about their differences.

B．The author is demonstrating some of the differences between them.

C．The author is discussing the result of different methodologies employed.

D．The author is trying to make some conclusive researches by himself.