Gas exchange occurs in the saclike structure called

Which mantle is under the crust the upper mantle or the lower mantle i think it's upper let me know if i'm right

Immature bone cells, or osteoblasts, manufacture a protein called osteoid as well as several hormones. because of this, we would expect osteoblasts to contain numerous a) nuclei. b) ribosomes. c) lysosomes. d) golgi bodies.

What do we call an individual that has inherited two identical alleles for the same trait? a.homozygous b.heterozygous c.monozzygous