虫垂（いわゆる盲腸）はムダじゃないかも。腸内細菌の"避難所"説と、手術しない治療

Q1. What is the passage mainly about?

1. AHow to eat healthy food
2. BWhy the large intestine is long
3. CNew ideas about the appendix
4. DHow animals lost their tails

役に立たないとされてきた虫垂についての新しい考え方がテーマなので C。

Q2. How long has the appendix stayed in mammals?

1. AFor over 80 million years
2. BFor about 80 years
3. CFor 2 million years
4. DFor only a few thousand years

stayed for over 80 million years とあるので A。

Q3. In this passage, "useless" means ...

1. Avery strong
2. Bhaving no purpose
3. Cvery small
4. Dvery famous

use（役に立つこと）＋-less（ない）で「役に立たない」なので B。

Q1. What did Smith's team find in 2009?

1. AThe appendix is found only in humans.
2. BThe appendix disappeared 80 million years ago.
3. CThe appendix causes many diseases.
4. DThe appendix evolved independently at least twice.

the appendix had evolved independently at least twice とあるので D。

Q2. According to the "safe house" idea, how might the appendix help?

1. ABacteria hiding there could help the gut recover after illness.
2. BIt produces medicine for the body.
3. CIt stores food for later.
4. DIt removes all bacteria from the body.

those hiding in the appendix could help the gut recover とあるので A。

Q3. Why does the writer say the long history of the appendix is important?

1. AIt proves that the appendix is dangerous.
2. BIt suggests that the appendix may be useful.
3. CIt shows that mammals are very old.
4. DIt explains why surgery is necessary.

Such a long history suggests that it may have a function. とあるので B。

Q1. What is the main point of the passage?

1. AThe appendix should always be removed.
2. BThe appendix is a completely useless organ.
3. CEvidence suggests the appendix may have a function, and appendicitis treatment is changing.
4. DAntibiotics never work for appendicitis.

虫垂に機能がある可能性と、虫垂炎治療の変化の両方を述べているので C。

Q2. Why does the author say the 2011 study gives only "indirect support"?

1. ABecause it was a retrospective association that cannot prove cause and effect
2. BBecause it studied animals instead of humans
3. CBecause it found no difference at all
4. DBecause it was about appendicitis surgery

this retrospective link cannot prove cause とあるので A。過去の記録をさかのぼって見つけた関連（retrospective link）は、原因の証明にならない。

Q3. According to the passage, what does "vestigial" actually mean?

1. AHaving no role at all
2. BBeing dangerous to health
3. CBeing newly evolved
4. DHaving lost its original role

最終文 "vestigial" means an organ has lost its original role, which is different from having no role at all とあるので D。