Researchers believe this results from its extremely hot atmosphere, which is as high as 1,800°F (980°C), 18 its closeness to its sun—its source of energy.
答案：(A) thanks to
【慣用語】thanks to 表示「由於／多虧」，說明大氣層高溫的原因是它距離恆星（能量來源）很近。regardless of（不論）、in addition to（此外）、in terms of（就…而言）皆不符合此處表因果關係的文意。
本題大考中心未公布逐題答對率，以下不談數據，只談觀念。
thanks to 這個組合，你的印象大概只有「感謝」兩個字，很難立刻想到它其實是在講原因；四個選項又都由兩三個字組成、長得像，容易憑語感挑。
先確認空格兩邊的關係。前面是 its extremely hot atmosphere（它極熱的大氣層），後面是 its closeness to its sun，而破折號後面作者把話講白了：its source of energy（那是它的能量來源）。離能量來源很近，所以非常熱——這是因果關係，空格要填的是帶出原因的說法。thanks to 的意思正是「由於、多虧」。特別要記的是它不帶好壞的感情色彩，壞事一樣能用：The game was cancelled thanks to the rain.（比賽因為下雨取消了），別被字面的 thanks 綁住。另外看這四個選項的共同身分：它們後面一律接名詞，整組當一個介系詞用，是多字介系詞而不是連接詞——連接詞後面接的是子句。這個分法有依據：劍橋 English Grammar Today 的 Prepositions 條目說 some pairs and groups of words operate like single prepositions，並把 because of、in place of、in addition to、in front of、up to 列為例子。
regardless of（不管、無論）表示不受影響，但這一句的高溫正是被距離影響的，方向剛好相反。in addition to（除了……之外，還）要求前後是可以相加的兩樣東西，但「離恆星近」不是與「大氣很熱」並列的另一件事，它是那件事的原因。in terms of（就……而言、從……的角度）用來限定討論的角度（in terms of cost），接在這裡讀不通。
thanks to（由於、多虧，不限好事）、regardless of（不管、無論）、in terms of（就……而言）、as high as（高達）、closeness to（與……的接近程度）、source of energy（能量來源）
Astronomers have discovered the darkest alien planet known to exist in the galaxy.
The Jupiter-sized planet, known as TrES-2b, is located in another solar system some 750 million light years away from Earth. Reflecting less than one percent of the sunlight 16 on it, TrES-2b is less reflective than black acrylic paint, and is blacker than coal. The only light that comes from TrES-2b is a faint red glow, 17 the heated coils on an electric stove or a very dim light bulb. Researchers believe this results from its extremely hot atmosphere, which is as high as 1,800°F (980°C), 18 its closeness to its sun—its source of energy.
So how does this planet manage to absorb about 99% of the light it receives from its sun? 19 researchers are not completely sure, they believe it could be because its atmosphere is composed of light-absorbing chemicals like vaporized sodium or even some elements whose existence is not yet known. Although they may never be able to 20 exactly how the planet remains so stealthily hidden, scientists are sure of one thing—there are many more even darker planets out there just waiting to be discovered!