Which statement is true?

the earth's moon is thought to have formed when a mars-sized planet collided with earth during its final stages of planetary accretion.
without the earth's moon, life on earth would not be possible.
the earth's moon is the smallest moon relative to its host planet.
the earth's moon is the same size as the earth.

In which situation has the independent variable for the experiment been changed? check all that apply. changed from counting the number of duckweed at day 0 and day 14 to counting them every day changed from testing duckweed growth in beakers to testing duckweed growth in large outdoor tanks changed from testing the effect of ph on duckweed growth to testing the effect of light levels on duckweed growth changed from testing the effect of acid ph on duckweed growth to testing the effect of basic ph on duckweed growth

The frequencies refer to the sample data collected from a population of interest when performing a hypothesis test comparing two or more population proportions.

What is the increase in density of a medium due to wave travel?