I would say:
<span>C.
present participle
I could be wrong though</span>
Loneliness is a universal human emotion that is both complex and unique to each individual. Because it has no single common cause, the prevention and treatment of this potentially damaging state of mind can vary dramatically.
For example, a lonely child who struggles to make friends at his school has different needs than a lonely old man whose wife has recently died. In order to understand loneliness, it's important to take a closer look at exactly what we mean by the term "lonely," as well as the various causes, health consequences, symptoms, and potential treatments for loneliness.
I hope this helps you
<span>The transition word is 'but' it allows the reader to understand there is another part to the sentence. That there is a cause and effect to the sentence.</span>
I'm not writing a whole essay for you but i can get it started,
Education has been the foundation of the modern age world because of the need to educate the youth of the world. Countries that live in poverty have no affordable education system or an education system at all. By making education free for everyone then society can move together as one instead of competing country against country to see which one is able to advance faster.