Students are experimenting with a substance that they think can be added to soil to increase the number of
flowers a certain plant will make. They set up 20 pots of
soil, each planted with the same type of seed. They
divide the pots into two groups and add 15 drops of the
substance to pots in one group and only 10 drops to pots
in the other group. After the plants grow for four weeks,
the students count how many flowers each plant has
made
What does this experimental investigation lack?
a control group
an independent variable
a dependent variable
a procedure

The earth's moon is unusually large. two popular theories of the moon's origin include the "sister world" hypothesis, which states that the moon formed from the same materials as the earth, near enough to the earth that they fell into orbit around each other. a second theory is the "capture" hypothesis, in which the moon formed elsewhere in the solar system, and the earth's gravity pulled it into its orbit. studies of what the moon is made of indicate that some of its materials had to come from the earth or from the same area of the solar system where the earth had formed. at the same time, the moon does not contain much of the material that makes up the earth's core, so the moon could not have formed from the same materials as the earth. how do the two facts above affect the described theories of the moon's origin? a. they show that scientists will never agree on where the moon came from. b. they show that more experiments on moon formation need to be done. c. they show that no theory accounts for the existence of the moon. d. they show that neither theory is complete and entirely correct.

Which of the following compounds does not contain molecules? question 2 options: co2 h2 nacl h2o

Which of the following statements is true? a. elements in the last period are radioactive. b. atomic weight is the same as atomic mass. c. elements in the same group have the same number of electron shells. d. atomic number equals the number of neutrons in the nucleus of an atom.