Read the given passage and answer the following questions -
Gravity is a fascinating force that we experience every day, yet it's so much more than just what keeps our feet on the ground. Imagine the universe as a vast stage, and gravity acts like invisible strings that pull objects towards each other. It's the reason why when you jump up, you always come back down.
This force works everywhere in the universe. It's what keeps the planets in our solar system orbiting around the sun. The moon orbits Earth because of gravity, and tides are created because of the gravitational pull between Earth and the moon. Even the stars and galaxies are held together by gravity.
Gravity depends on two main things: the mass of objects and the distance between them. The more massive an object is, the stronger its gravitational pull. That's why Earth, being much larger than a basketball, has enough gravity to keep us grounded. Also, the closer objects are to each other, the stronger the pull of gravity. This is why astronauts feel weightless in space; they are far away from the Earth's surface, reducing the gravitational pull they experience.
Even though gravity is everywhere, its strength can vary. For example, gravity on the moon is weaker than on Earth, which is why astronauts can jump higher there. Understanding gravity is crucial for space travel and many other scientific endeavors. It's a key player in the universe, affecting everything from the fall of an apple to the motion of planets.
Identify the part of speech for the underlined word in the following sentence from the passage:
"Gravity depends on two main things: the mass of objects and the distance between them."