Chemical And Industrial Accidents What Is The Flaw In This Argument And Explain Why For Your Choice. Thanks?

What is the flaw in this argument and explain why for your choice. Thanks? - chemical and industrial accidents

Human error is the cause of at least three major disasters identified - the nuclear disaster at Chernobyl and Three Mile Iceland and the leakage of chemicals in a factory in Bhopal. If you have lack of sleep is responsible for these errors can be expected to occur during the night shift, instead of the time during the workday, because it was found that night workers sleep an average of two hours less per day as a laborer. In fact, in each case, the critical errors are to be 3 hours, so sleep deprivation, the cause.
Which of the following are the errors in the above argument?

It is assumed that human error is not the cause of these disasters.
B it is assumed that people who do not sleep the night work during the day.
C is assumed that fatigue cause of major accidents.
D is working pressure is heavier for night workers to day laborers.
E is assumed that errors have occurred during the night, if not the workers suffer from lack of sleep.