Question

1. which sentence from the section \stars differ in size, brightness and color\ supports the idea that stars burn out? (a) although stars like these were common in the early universe, today... (b) the larger a star, the shorter its life. (c) they have lifetimes of only a few million years. (d) when a star runs out of fuel, the heat within it starts to fade. 2. read the paragraph from the section \from clouds of dust and gas a star is born! during its adulthood, a star is a balancing act between two forces. the first is the pull of gravity. it tries to squeeze the star into the smallest and tightest ball possible. the second is the tremendous heat and pressure from the stars core, which tries to push material outward. that keeps the star from collapsing under its own weight. it also creates the energy that makes the star shine. what is the main idea of this paragraph? (a) an adult star can collapse beneath its own weight at any time. (b) stars shine because they are squeezed by gravity into a small ball. (c) a star is held together by forces that push and pull against each other. (d) the core of a star is a small circular ball that gives it shape and shines. 3. what is the main idea of the section \from a nova to a supernova\? (a) once a star dies, it can pull material from nearby stars causing it to grow. (b) the core of a dead star can collapse and create a large explosion. (c) stars can grow by pulling material from other stars even after they die. (d) stars never truly die, but continue to grow by pulling matter from other nearby objects. 4. which sentence from the section \supernova explosions and black holes\ shows how the death of a star can influence other objects around it? (a) on average, a supernova explosion occurs about once every hundred years in an ordinary galaxy. (b) most supernova explosions are too far away to be seen without a telescope. (c) the gravity of a black hole is so strong that nothing can escape it, not even light. (d) the material left behind by these stars eventually blends with gas and dust.

Explanation:

1. Analyze each option in the context of the section "Stars Differ in Size, Brightness and Color" to find which sentence supports the idea that stars burn out. Option C mentions short - life spans which implies they burn out.
2. For the paragraph about a star in adulthood, the main idea is the balance of forces (gravity pulling in and heat/pressure pushing out) that keep the star stable. Option D reflects this balance.
3. In the section "From A Nova To A Supernova", the main idea is about how stars can grow by pulling material from other stars even after they die. Option D captures this concept.
4. To show how the death of a star can influence other objects around it, the gravity of a black hole (formed from a star's death) being so strong that nothing can escape it (including light) in option D shows this influence.

Answer:

1. C. They have lifetimes of only a few million years.
2. D. The core of a star is a small circular ball that gives it shape and shines.
3. D. Stars never truly die, but continue to grow by pulling matter from other nearby objects.
4. D. The material left behind by these stars eventually blends with gas and dust.