I think I understood the main idea behind naming compounds with carbonyl groups, however I am not sure about a few things.
For the first compound, there is more than one carbonyl group and one of them is in the end of the chain. I am trying to decide between 2-oxopropanal and propana-1,2-dione.
For the second one, I am not sure what happens if there are two oxygens attached to a carbon atom with a double bond. I am trying to decide between methanedione and methanedial.
I am not sure about this because one definition of aldehydes I have heard is when the carbon atom is attached to a hydrogen as well as the oxygen. And the other is if it is in the end of the chain.
And the final compound that I am not sure about is when there are two hydroxyl groups attached to the carbon as well as an oxygen with a double bond. I think it is hydroxymethanoic acid, but I am not completely sure.