The time when sunlight is visible

A satellite completes one full orbit around Earth. The work performed by Earth's gravitational force on the satellite is

A) always positive. B) zero J. C) always negative. D) positive most of the time. E) negative most of the time.

Elliptical galaxies, with older stars, will be more likely to have evolved intelligences than the stars close to us in the Milky Way

Indicate whether the statement is true or false

Why is Saturn almost as large in radius as Jupiter despite its smaller mass?

A) Jupiter's greater mass compresses it more, thus increasing its density. B) Saturn's rings make the planet look bigger. C) Saturn is farther from the Sun, thus cooler, and therefore less compact. D) Saturn has a larger proportion of hydrogen and helium than Jupiter, and is therefore less dense. E) Jupiter's strong magnetic field constrains its size.

Why do almost all active galaxies occur in clusters of galaxies?

What will be an ideal response?