Question

1. choose the best answer.

astronomers use ______ to measure the great distances in outer space because other measures are hard to understand.
options: milliseconds, light - years, trillions, megawatts
scientists estimate that there could be as many as 200 billion ______ in the universe.
options: planets, galaxies, asteroids, meteors

Explanation:

For the first question (Astronomers use ___ to measure great distances in outer space), we analyze the options:

• Milliseconds: unit of time, not distance.
• Light - years: defined as the distance light travels in one year, a standard unit for astronomical distances.
• Trillions: a number, not a distance unit.
• Megawatts: unit of power, not distance.

For the second question (Scientists estimate as many as 200 billion ___ in the universe), we analyze:

• Planets: too few compared to 200 billion scale for the universe.
• Asteroids: also too few in number at this scale.
• Meteors: not in the 200 billion scale for the universe.
• Galaxies: Current estimates suggest there could be around 200 billion (or more) galaxies in the observable universe, making this the correct choice.

Answer:

First question: The option with "light - years" (the third option from the top left).
Second question: The option with "galaxies" (the third option from the top right).