Answer:
C) Quality of life
I dont think its any of the others
It shows that the value of education can increase return on investment
The word <em>over </em>is used as an adverb in this sentence.
If the sentence said - There will be clouds over most of the country, then it would be a preposition.
B) Problem and Solution
We can suggest this as the correct answer because of the hint words 'issues', 'conflicts' and 'resolved' in the question, as they are synonyms or related to the words 'problem' and 'solution'. ☺
I don't seem to understand your question
