Both B and D are correct forms - the last comma is optional.
I would use probably use a comma here because the brothers' tasks are so diverse. However, I am not forced to use it - it is optional.
I would not use it here:
I am considering a HP, Dell and Lenovo as possibilities for my next computer.
(Because they are not diverse - they are all brands of computers).
What's wrong with A - It sound as if your brothers dropped the dishes as they took them out of the dishwasher and had to clean up all those broken washed dishes.
C is wrong because of the unecessary common after the "and".
some considerations you should have of your audience would be who your audience is, is it business is it a reunion, exc. you would adjust the content to your audience by making sure it is put in a way they will understand. especially if it is a persuasive speech you want to make them believe your point of view. if your audience was president of the college you would need to change your speech to be as professional as possible.
