Answer:
The answer is indeed letter E) learn how and why things happen in our world.
Explanation:
In the original sentence, there is a wordiness problem. Wordiness happens when writers use more words than necessary to say something. It can involve repetition of terms - which is the case here - or redundant expressions. In the sentence "Experiments help scientists learn how things happen in our world and why things happen in our world," there should be no need to repeat the phrase "things happen in our world". All we must do is find a way to say the same thing, but using that phrase only once. We must try to keep it simple; it will be of no use if we remove that phrase but add too many words in its place.
Letter A - is not totally incorrect, but it also has a wordiness problem;
Letter B - is incorrect; there is no need to use "both" and "as well as" together;
Letter C - same as A, too many words;
Letter D - incorrect; changes the original meaning when it uses "but not why";
Letter E - is perfect. It uses the phrase "things happen in our world" only once and keeps the connection simple by employing the conjunction "and".
