The sentence that represents the main idea of the passage is: "Many cultures remember those who have died with formal observances and festivals. " Option B is correct.
The main idea of this topic is the fact that in different countries, certain festivals or observance are celebrated with the purpose of honoring and commemorating death people. Because of that, the text mentions and describes specific events in some countries such as El dia de los Muertos celebrated in Mexico and the festivals in the Far East, as well as the Memorial Day carried out in the United States to honor military members who lost their lives,