I believe the answer is B: Earth's oceans absorb some of the carbon dioxide from the atmosphere.
The double membrane. It's theorized that chloroplasts used to be their own single-celled organism in the environment (and therefore with its own membrane). Then, the theory states, a larger cell took in the chloroplast by endocytosis, which involves surrounding the chloroplast in the large cell's own membrane. The chloroplast would then have two membranes surrounding it. This is similar to the thinking for mitochondria becoming an organelle as well. Hope this helps! :)
AB blood type is an example of codominance. It is a type of dominance where alleles of a pair are fully expressed. This would result to a product that is neither recessive not dominant and an AB blood type is a perfect example.
hope this helped
