The irony is that they are smiling with “torn and bleeding hearts”.
The idea it emphasizes is that they are smiling to hide their pain.
The overall message revealed by the irony is that they are in considerable emotional turmoil and faking happiness to mask their distress.
The correct answer among all the other choices is A)We cannot do as much as the soldiers have done. This is the best paraphrase of this quotation from Abraham Lincoln's Gettysburg Address. Thank you for posting your question. I hope this answer helped you. Let me know if you need more help.