Put one suitable word in the blanks

Question V: A- Put one suitable word in the blanks. A popular theory explaining the evolution ..1.. the universe is known as the Big Bang Model. According ..2.. the model, at some time between ten ...3.. twenty billion years ago, all present matter and energy were compressed into a small ball only a few kilometres in diameter. It was, in effect, an atom …4… contained in the form of pure energy all of the components of the entire universe. Then, at a moment …5..time that astronomers refer to as T = 0, the ball exploded, hurling the energy …6…space. Expansion occurred. As the energy cooled, most …7….it became matter in the form of protons, neutrons and ….8…. These original particles ….9…to form hydrogen and helium, and continue to expand. Matter formed into galaxies with stars and …10.