Explanation:

In the sentence, the words “expected” and “only” imply that the data received from the spacecraft exceeded scientists’ expectations. Therefore, the words that fill the blank
should describe a reaction to results that are better than hoped for, and the choices “thrilled about” and “elated by” both express such a reaction. The scientists may well
also have been eager for, or keen on, the information, but their eagerness is not well explained by the unexpectedness of the information.
Thus, the correct answer is thrilled about (Choice C) and elated by (Choice E).
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i selected eager and keen..i fall in trap

Answers :C,E

C, E

As per my understanding, since the outcome was more than expectation therefore, scientists were thrilled and elated (option C and E)
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The crux of all SE questions lies in understanding the meaning it intends to convey. I consider them as reading comprehension questions. Read to understand the real meaning and then fill in for the blank.
In this question- what the voyger did was beyond its scope hence the mentioned reaction

The scientists only expected the voyager to give info about 2 planets so they were elated when they received more than expected. So C and E

A,E

You didn't read the sentence thoroughly then! You can only be eager or keen for something you are anticipating. The sentence makes it clear that the scientists were not expecting the information about Neptune. Hence C and E are the answers.

It was surprising when I understood that the verb "to thrill" means "to excite or please sb very much." This is an elementary word and I never looked up in the dictionary before, because I have always been sure that Thriller Movie is a frightening movie:)). So, I chose keen instead of thrilled. However, with the wealth of information after twelve years from far distances in solar system, I believe that scientists should be keen on the unknown information rather than thrilled.