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! :)
We administered 300 mg of clindamycin intravenously at 12-h intervals for 2 days to patients with acute and chronic hepatitis, cirrhosis, and controls to determine whether clindamycin will exacerbate preexisting hepatic dysfunction or whether drug excretion will be delayed in patients with liver disease