I would say it is answer choice C, Laws are based on proven hypothesis by many different scientists.
Answer: Hydrogen and Helium
Explanation: Hydrogen is made from from one proton and one electron, making them one of the simplest forms of elements in the universe. Combining hydrogen atoms creates helium, the second most common element in the Universe.
He thought elements that haven't been discovered belonged in the place of the gap. He could also use the atomic mass of the missing elements
Water molecules move througout the solute