Qusetions 21-25 are based on the following passage: In the past,degrees were very unusual in my family.I remembeer the day my uncle graduated.We had a huge party,and for many years my mother called him"the genius"and listened to his opinion.Today in comparison,five of my brothers and sisters have degrees,and two are studying for their masters'.However,some people think that this inctreased access to education is devaluing degrees. People have several agruments against the need for degrees.They say that having so many graduates devealues a degree,People lose respect for the degree holder.It is also claimed that education has become a rat race.Graduates have to compete for jobs even after years of studying.Another point is that studying for such a long time leads to learners becoming inflexible.They know a lot about one narrow subject,but are unable to apply their skills.Employers prefer more flexible and adaptable workers. However,I feel strongly that this move to having more qualifications is a positive development.In the past education was only for the rich and powerfull.Now it is available to everyone,and this will have many advantages for the country and the individual.First of all,it is impossible to be overeducated.The more people are educated,the better the world will be,because people with degrees have many more opportunities.They can take a wider variety of jobs and do what they enjoy doing,instead of being forced to take a job they dislike.Finally,a highly educated workforce is good for the economy of the country.It attracts foreign investment. In conclusion,although there are undoubtedly some problems with increased levels of education,I feel strongly that the country can only progress if all its people are educated to the maximum of their ability. What is the author's purpose of writing this passage（）

A. To explain a complicated idea.
B. To argue about a disputed issue.
C. To describe a social phenonmenon.
D. To demonstrate a research result.