The correct option is A learn from other people's struggles
As mentioned in the first paragraph, "They tell us that no matter what personal difficulty or sorrow we may be facing, there is always light at the end of the tunnel... Walt Disney... Steve Jobs... Beethoven... All these people have one thing in common; they faced numerous rejections yet refused to listen to the discouraging things people said.", the focus is put on people who struggled their way up.
These inspirational stories tell us that we should learn from other people's struggles: "They give people strength to believe that despite all odds, they could accomplish great things."
Option A explains the same thing, hence A is correct.
Option B: The passage does not mention nor imply this line: try to achieve simple things. Instead, it's mentioned in the passage: "It is only through adversity that any person has ever achieved greatness."
Achieving 'simple things' is the opposite of what the passage is about.
Hence B is incorrect.
Option C: This line is not mentioned nor implied. The problems are not remarkable, but the stories of inspirational people are:
"Stories of inspiration about people who have achieved great things even when they faced adversity are remarkable."
Hence C is incorrect.
Option D: This means vague, and isn't implied by the passage. The given passage does not focus on 'chances' but on the struggle that has to be faced to achieve greatness. Hence option D is incorrect.