Directions: In the following passage, some of the words have been made bold, each of which is preceded by a letter. Find the suitable word from the options given below that could replace the bold word so as to make the paragraph meaningful.
After years of ___ A ___ disputed over whether Pluto is a planet, in 2006 the International Astronomical Union (IAU) voted to remove Pluto’s planetary status. Now some researchers are ___ B ___ validating this decision, citing the manner in which scientific tradition has dealt with the taxonomy of planets. The IAU, in 2006, designated Pluto a ‘dwarf planet’ along with Ceres in the asteroid belt and Xena, an object in the Kuiper belt, which is an icy ring of frozen objects that circle the solar system beyond Neptune’s orbit. It was a bid to overcome sentiment and go by scientific ___ C ___ reflection . The meeting defined three conditions for a celestial object to be called a planet: one, it must orbit the Sun; two, it should be massive enough to acquire an approximately spherical shape; three, it has to ‘clear its orbit’, that is, be the object that ___ D ___ excerpts the maximum gravitational pull within its orbit. Owing to this third property, if an object ventures close to a planet’s orbit, it will either collide with it and be accreted, or be ejected out. However, Pluto is affected ___ E ___ at Neptune’s gravity. It also shares its orbit with the frozen objects in the Kuiper belt. Based on this, the IAU deemed that Pluto did not ‘clear its orbit’. Dwarf planets, on the other hand, need only satisfy the first two conditions.
This rationale has been questioned by Philip Metzger, a planetary physicist who has worked with the U.S. National Aeronautics and Space Administration, and others who have studied the history of classifying planets and come up with several ___ F ___ abnormal to the third rule. In a paper published in the journal Icarus, they point out that the only work in history that used this rule to classify planets was an article by William Herschel in 1802. They also argue that this work was based on reasoning and observations that have ___ G ___ because been disproved. However, the last argument does not build up a strong enough case to give up what is, in fact, a sensible rule. Physics has many examples where an idea was once ___ H ___ jeopardized for being incorrect, and much later emerged in a different form and gained acceptance — the concept of photons, for instance. And then again, if Pluto were to be re-designated a planet, many more complications would ___ I ___ dwell . For one thing, Charon, Pluto’s moon, is much too large to be called a satellite. Judging by this, the Charon-Pluto system should then rightly be called a binary planet system. This would then lead to classifying several other sets of bodies as binary planets. Recent research shows that both the Kuiper Belt and the Oort cloud, a shell of objects that surrounds the entire solar system far beyond the Kuiper belt, contain objects that can then be called planets, thereby complicating the issue. Denying planetary status to Pluto is then nothing less than a sweep of Occam’s razor, and Pluto remains a dwarf planet, ___ J ___ all an exceptional one.