For thousands of years, people have
written down when they saw comets.
why are some comets seen only once
but others are seen more than once?

Which evidence is most likely used to indicate the beginning of solar system formation? a. materials combined to form a mass. b. materials were pulled together by gravity. c. water condensed and collected to form oceans. d. different species of microorganisms lived on earth.

In the diagram below, ab and bc are tangent to o. what is the measure of

Which country in the video has the highest population growth rate?