Detailed Instructions: You are given a paragraph, a question and some answer options (associated with "A", "B", "C", "D", etc.) You need to list all the correct answer options with their associated letters (e.g. "A" can be a valid answer). Note that sometimes, more than one option can answer the question correctly and completely. In those cases, please generate all such options separated by a comma (e.g. "A, B" is a valid answer). Do not generate anything else apart from one or more of the following characters: 'A', 'B, 'C', 'D', etc.
Problem:Paragraph- Sent 1: (CNN) -- Declaring 2010 "The best year in safety performance in our company's history," Transocean Ltd., owner of the Gulf of Mexico oil rig that exploded, killing 11 workers, has awarded its top executives hefty bonuses and raises, according to a recent filing with the U.S. Securities and Exchange Commission.
Sent 2: That includes a $200,000 salary increase for Transocean president and chief executive officer Steven L. Newman, whose base salary will increase from $900,000 to $1.1 million, according to the SEC report.
Sent 3: Newman's bonus was $374,062, the report states.
Sent 4: Newman also has a $5.4 million long-term compensation package the company awarded him upon his appointment as CEO in March 2010, according to the SEC filing.
Sent 5: The latest cash awards are based in part on the company's "performance under safety," the Transocean filing states.
Sent 6: "Notwithstanding the tragic loss of life in the Gulf of Mexico, we achieved an exemplary statistical safety record as measured by our total recordable incident rate and total potential severity rate," the SEC statement reads.
Sent 7: "As measured by these standards, we recorded the best year in safety performance in our Company's history."Sent 8: The company called that record "a reflection on our commitment to achieving an incident-free environment, all the time, everywhere," the SEC filing states.
Sent 9: The company did not respond to an e-mail from CNN seeking comment.
Sent 10: The April 20, 2010, explosion on the Deepwater Horizon rig injured 17 workers and killed 11 others, including nine Transocean employees, according to the SEC filing.
Sent 11: It has been called the worst spill in U.S. history.
Sent 12: The well was capped three months later, but not before millions of barrels of oil spilled into the Gulf.
Sent 13: In January, President Barack Obama's National Commission on the BP Deepwater Horizon Oil Spill and Offshore Drilling released a report that spread blame for the accident among Transocean, BP -- which leased the rig -- and Halliburton, which installed the rig's cement casing. 
Question: On what date did the worst oil spill in US history occur? (A) March, 2010 (B) 20th April 2010 (C) 11-17-2010 (D) April 19 2010 (E) April 20, 2010 (F) 21st April 2010.
Solution:

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
user
B, E.