The appearance of the star Gamma Cephei varies regularly. The existence of a planet circling a star can cause regular variation in its appearance. However, the regular variation in Gamma Cephei`s appearance is no reason to think that there is a planet circling it, since the slow rotation of a star can also cause its appearance to vary regularly and ____________.
Which of the following most logically completes the argument?
- Amany stars that have planets circling them rotate slowly
- BGamma Cephei varies more in appearance than many other stars do
- Cit is easier to determine the speed at which a star rotates than to determine whether a planet is circling it
- Danalysis of sunspot activity on Gamma Cephei shows that it rotates slowly
- EGamma Cephei is only one of many stars that vary regularly in appearance
답은 D인데 sunspot(흑점)에 대한 정보나 언급이 하나도 없는데 D가 답인게 이해가 잘안가서요.
다른 게 특별히 답으로 생각되진 않지만 D도 이해가 잘안가네요.
sunspot에 특별히 의미를 부여할 필요는 없다고 생각되지만 rotates slowly가 어떻게 이어지는 걸까요?