In which order did the events forming our solar system occur?

the solar nebula became hot and dense pulling in more gas. this flattened into a rotating disk. it spun faster and faster, forming the sun.
gas was pulled toward the center, forming the sun. gas flattened into a rotating disk and became hot and dense, forming a solar nebula that spun faster and faster.
gas flattened into a rotating disk and became hot and dense, forming a solar nebula that spun faster and faster. gas was pulled toward the center, forming the sun.
the solar nebula spun faster and faster and flattened into a rotating disk. most of the gas was pulled toward the center, where it became hot and dense, forming the sun.

answer : one can design an experiment using a liquid and an additive that can be added to the liquid and observe the chemical changes in the reaction species.

one would need a beaker which is filled with a known amount of the liquid in which thermometer is placed to measure the temperature changes; after addition of the additive to the liquid solution one can note down the temperature change and find whether the reaction is endothermic or exothermic in nature. by subtracting the initial temperature value with the final temperature one can find the temperature changes.

various combinations of liquid and additive can be used. liquid in this case can be a known quantity of water and additives can be epsom salt or without epsom salt the experiment can be conducted to notice the changes. water and ice, hydrogen peroxide and dry yeast, vinegar and baking soda,etc.

a is the correct answer