Easy to come easy to go. They are pretty wise words. It teaches us that shortcuts don't always work. You need to work hard to a achieve something. If you don't that something won't take time to turn into nothing. And something is better than nothing. So it's better if you work hard to achieve something even though you will receive it a little later but it will definitely last longer than your shortcuts will. Send if u want something to last forever you shouldnt rush into it. So it's better you don't take the easy way and let it go easily in place take a difficult way and later be proud of achieving your goal and making it last forever. Before rainbow there is always a storm. Before the sun rises there is always dark. But there are some stars you don't find them in the sun rays even though they are there, to find out the star in yourself you need to pass the dark which is as good as difficulty.
The quote by Martin Luther King Jr. means that the value or character of a man is related to the courage he demonstrates in difficult times when he knows he owns the truth and must endure in spite of the obstacles he is facing. King said this words in his last speech during the Civil Rights Movement, before he was assassinated in 1968.
All the other options are quotes from specific parts and does not directly tell us about or gives a summary of what the book is about, therefore no central idea. A gives us a glimpse into the story.