阅读下列短文，从每题所给的A、B、C和D四个选项中，选出最佳选项。
A
Previous studies of children have found links between use of electronic media and physical health risks. Electronic media use is also associated with social connection. However, comparatively less is known about links with academic performance.
To help clarify these links,Mundy and colleagues studied 1,239 8-to 9-year -olds in Melbourne, Australia. They used a national achievement test data to measure the children's academic performance at baseline and again after two years. They also asked the children's parents to report on their kids' use of electronic media.
The researchers found that watching two or more hours of television per day at the age of8 or9 was associated with lower reading performance compared to peers two years later;the difference was equal to losing four months of learning. Using a computer for more than one hour per day was linked to a similar degree of lost numeracy（计算能力）.The analysis showed no links between use of videogames and academic performance.
By accounting for baseline academic performance and potentially influencing factors such as mental health difficulties and body mass index(BMI) and controlling for prior media use,the researchers were able to identify television and computer use was associated with poorer academic performance.
These findings could help parents and teachers better plans and clinical recommendations for electronic media use in late childhood. Future research could build on these results by examining continued associations in secondary school.The authors add:“The debate about the effects of modern media on children's learning has never been more important given the effects of today's Covid-19 on children. This is the first large study of electronic media use and learning in primary school children,and results showed heavier users of television and computers had significant declines in reading two years later compared with light users.”
21.What is Mundy's study mainly about?
A.Electronic media B.Acquisition approaches
C.Kids'health D.Academic performance
22.Which of the following statements may the author agree with?
A.Previous studies are inaccurate and unreliable.
B.Kids' capacity to read declines when they apply e-books.
C.Kids playing videogames can perform as well as before academically.
D.Watching TV will have a negative impact on kids merely within two years.
23.What makes the effects of modern media on children's learning a hot issue?
A.Challenges from public health B.Clinical recommendation on leisure
C.Parents'concern about future D.Tight schedules at schools
24.How did the researchers make the new discovery?
A.By inferring from previous studies
B.By referring to the national achievement test data
C.By analyzing children's mental health difficulties
D.By comparing academic performances before and after
