A) Roughly three times farther away than Pluto, the new planet is the most distant known object in the solar system, near-infrared spectra show signs of methane ice on the planet's surface, indicating that the planet has not been warmed significantly since the birth of the solar system some 4.5 billion years ago. — Elikinate. Comma splice. Two ICs need a FANBOYS conjunction or a semi colon to be joined together. (Solar system, near)
B) Roughly three times farther away than Pluto, the new planet is the most distant known object in the solar system, and near-infrared spectra show signs of methane ice on the planet's surface, which indicates that the planet has not been warmed significantly since the birth of the solar system some 4.5 billion years ago. — Elikinate. “Which” modifies planets surface and hence leads to an illogical meaning. Present participle present the result of previous clause is better.
C) Roughly three times farther away than Pluto, the new planet is the most distant known object in the solar system, and near-infrared spectra show signs of methane ice on the planet's surface, indicating that the planet has not been warmed significantly since the birth of the solar system some 4.5 billion years ago. — correct.
D) Roughly three times farther away than Pluto, the new planet, the most distant known object in the solar system, and near-infrared spectra show signs of methane ice on the planet's surface, indicating that the planet had not been warmed significantly since the birth of the solar system some 4.5 billion years ago. — When “since” is used, use present perfect “has been”. This choice uses “past perfect” leading to an illogical meaning.
E) Roughly three times farther away than Pluto, the new planet is the most distant known object in the solar system, near-infrared spectra show signs of methane ice on the planet's surface, indicating that the planet had not been warmed significantly since the birth of the solar system some 4.5 billion years ago. — same as D. Eliminate.
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