Sulfer is in the 3rd period of the periodic table meaning that 2 periods came before it hence the 2 electron shells and it is in the 6th group hence the 6 valence electrons.
Using this logic we know that the element in the 5th period and the 7th group which would be Iodine
We also know that the element in the 4th period and 8th group is Krypton
The Lewis dot model is more commonly used to show chemical reactions, I haven't heard of the addition or subtraction models before so there's a chance that it may only be part of your curriculum, or they are answers made up for your multiple choice.
In photosynthesis, solar energy is harvested as chemical energy in a process that converts water and carbon dioxide to glucose. Oxygen is released as a byproduct.
