Which statement about earth's layers is true?
oa.
they all consist of liquid rock.
b.
they each vary in size and temperature.
c. they are all under an equal amount of pressure.
d. they will soon combine, forming a single, thick layer.

African penguins, which inhabit the coasts of southern africa, were classified as an endangered species in 2010. two significant threats to their survival are ecosystem damage from oil spills and overfishing by humans. overfishing depletes the food supply of african penguins. the best method to reduce the threat of overfishing would be to . the risk of oil spills could be reduced by increasing the use of , which should oil consumption. if an oil spill does occur, could be used to remove the oil so the ecosystem may more quickly recover.

Why did mendel use pea plants in his experiments? a. they have no alleles. b. they are haploid organisms. c. they reproduce quickly. d. they are all male.

Can a trait be both polygenic and have multiple alleles? explain why or why not.