The correct sentence is "facts and opinions are not necessarily in opposition". That is so because one can agree with a fact.
On the other hand "fact" may not be a synonym of "opinion". In research you can use "facts", "opinions" or both. It is so because one does not exclude the possibility of using the other. They are not necessarily anthonyms/ opponents. an opinion is not more important than a fact, but on the contrary, because facts can be proved easier than opinions.
The only preposition in this sentence is the word of.
So based on your question that states a few trees in garden and one of them is a pear tree, there are pears. But a strong wind blew, there were neither pears on the tree nor on the ground. I think the best explaination to this statement is that some one might pick up the pear tree or it can be that its the wrong tree that is blown.
The answer is b, the students used their power to harm others
