Which of the following best describes half-life? a. half the time it takes for all of the nuclei in a sample of a radioactive isotope to decay. b. the time it takes for the nucleus of one atom of a radioactive isotope to split in half. c. the time it takes for half of the nuclei in a sample of a radioactive isotope to decay. d. the time it takes for the nucleus of one atom of a radioactive isotope to decay.

The fruit of a certain plant is sweet and fleshy. the seeds of this plant have a seed coat that is fairly tough. the seeds germinate better if they are exposed to acid, or scarification. what is the most likely type of dispersal for this seed? water animal wind

What characteristic makes a cell membrane selectively permeable

Select the correct answer. which of the following statements is a scientific claim? a. the early solar system had large amounts of water; so, the oldest objects in the solar system should also be abundant in water. b. the mass of the universe is much greater than current models predict; it is not possible to explain this inconsistency. c. planet earth is abundant in water, but there is no way to scientifically determine from where earth's water originated. d. earth is shaped like a sphere even if not all of the scientific observations related to its shape support this idea.