脳の半分を取り除く手術を受けた子どもたち。その後、残った半分の脳で何が起きていた？

Q1. What is the passage mainly about?

1. AHow to take medicine for headaches
2. BSurgery that removes half of the brain to treat serious seizures
3. CWhy children like going to school
4. DHow to make the brain bigger

重い発作の治療として脳の半分を取り除く手術が話題なので B。

Q2. What happens to many of these children after surgery?

1. AThey stop having seizures.
2. BThey lose all their memories.
3. CThey cannot talk at all.
4. DThey need the same surgery again.

many of these children stop having seizures とあるので A。

Q3. What does the last sentence, "Half a brain is not 'no problem,'" mean?

1. AHalf a brain works better than a whole brain.
2. BThe surgery is very easy.
3. CThe children never go to school.
4. DThe surgery can still leave difficulties.

直前に体の片側が動かしにくい・結果に個人差がある、とあるので「問題が残ることもある」の D。

Q1. Who mainly receives this operation?

1. AAdults who want to improve their memory
2. BChildren with severe epilepsy that medicine cannot control
3. CPeople with headaches
4. DAthletes with head injuries

children whose severe epilepsy cannot be controlled with medicine とあるので B。

Q2. What percentage of the 71 children no longer had seizures?

1. A49 percent
2. B54 percent
3. C65 percent
4. D71 percent

Sixty-five percent no longer had seizures とあるので C。71は人数。

Q3. Why might different networks be more strongly connected in these adults?

1. ATo share the extra work in the remaining half of the brain
2. BBecause they had more seizures
3. CBecause they took more medicine
4. DBecause their brains grew back

perhaps to share the extra work とあり、半分の脳で多くの役割をこなすためと考えられるので A。

Q1. Which statement best summarizes the passage?

1. AHemispherectomy has no side effects.
2. BAdults recover from hemispherectomy better than children.
3. CHalf of the brain is never enough for daily life.
4. DHemispherectomy often stops seizures and the remaining half can adapt, but there are costs and limits to the evidence.

発作が止まることが多く、残った半球が適応する一方、後遺症（The operation has real costs.）や研究の限界もある、というまとめなので D。

Q2. What did the 2019 Caltech study find in the remaining hemisphere?

1. ALanguage networks had disappeared.
2. BNetworks were organized much as in typical brains, but links between networks were stronger.
3. CThe remaining half had grown to the size of a whole brain.
4. DConnections between networks were weaker than usual.

networks ... were organized much as in typical brains とあり、Connections between different networks were stronger と続くので B。

Q3. Why may the six adults not represent all patients?

1. ABecause they had surgery as adults
2. BBecause they all had Rasmussen encephalitis
3. CBecause they were high-functioning volunteers
4. DBecause they were scanned at Johns Hopkins

The six were high-functioning volunteers, so they were not a representative sample とあるので C。選択バイアスの指摘。