Think about the article. the reader can tell that

a) other planets have more total solar eclipses than earth does.
b) solar winds will soon stop flowing out of the sun's upper atmosphere.
c) scientists believe it's important to know why the sun's atmosphere is hot.
d) most scientists don't care too much about total solar eclipses.
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The answer here is C, and that is why the scientists take the time to study the sun

 [C]:  

   "Scientists believe it's important to know why the sun's atmosphere is hot."

Note:  Consider:

Choice [A]:  "Other planets have more total solar eclipses than Earth does."
    This choice is INCORRECT;  since nowhere in the article is this mentioned or implied; nor can this be inferred.

Choice [B]:  "Solar winds will soon stop flowing out of the sun's upper atmosphere." 
    This choice is INCORRECT.  Note that "solar winds" are mentioned in the last paragraph of the article.  But the article never mentions or implies that the solar winds will "soon stop flowing out of [the sun's upper atmosphere]".

Choice [D]:  "Most scientists don't care too much about total solar eclipses."
    This choice is INCORRECT.  To the contrary, this article emphasizes that scientist are very interested in "total solar eclipses".  Refer to the beginning sentence of the third paragraph—which occurs after the first two paragraphs discussing "total solar eclipses" and a particular "total solar eclipse" :  
       "Scientists were excited. ..." .

The remaining—and correct—answer choice is:

Answer choice:  [C]:  "Scientists believe it's important to know why the sun's atmosphere is hot."  
      Note:  The third paragraph of this article directly emphasizes this.