Read the following passage, then choose the correct answer.

Planet earth is part of a system of planets and their moons, as well as numerous asteroids and comets which (1) _________around a huge star we call the Sun. The Sun itself (2) _________of gas. Nuclear reactions inside its core (3) _______the heat and light that make life on the Earth (4) ________. The Earth is the third of four small terrestrial (Earth like) planets that orbit close to the (5) _________. Further out in our Solar System are four huge gas planets, while distant Pluto, (6) _________planet, is made (7) _________rock and ice. Our Earth is one of the ten planets that orbit the Sun- a huge, burning-hot star in the center of our Solar System. The Solar System and all the stars in the (8) _________are part of our galaxy-the Milky Way, which (9) ________as many as 200 billion stars. Beyond our galaxy (10) _________millions more galaxies. They all add together to make up the Universe.

Planet earth is part of a system of planets and their moons, as well as numerous asteroids and comets which (1) _________around a huge star we call the Sun.