An international team of astronomers working at telescopes in the Canary Islands and Spain has detected at least 18 huge gas spheres estimated to have 5 to 15 times the mass of Jupiter, the solar system's largest planet.

(A) astronomers working at telescopes in the Canary Islands and Spain has detected at least 18 huge gas spheres estimated to have 5 to 15 times the mass of Jupiter

(B) astronomers working at telescopes in the Canary Islands and Spain has detected at least 18 huge gas spheres estimated to be 5 to 15 times Jupiter's mass

(C) astronomers is working at telescopes in the Canary Islands and Spain, having detected at least 18 huge gas spheres that are estimated at 5 to 15 times the mass of Jupiter

A的比较对象是谁跟谁，prep的解释说C gas spheres不能与the mass of Jupiter作比较，难道A不是这2个词的比较吗？

这题主要考点是同位语 - the mass of Jupiter, the solar system's largest planet。

我觉得这里不是比较的问题，estimated to have 5 to 15 times the mass of

Jupiter前应该省略了一个that，是修饰gas spheres的大小的，后面是Jupiter的同

位语，C的问题在于wordy，跟比较对象没关系