These are all caused by viruses.
I believe the bone system that red marrow belongs to is D. Skeletal system.
b
I am not that sure but I think endocrine cell don't contain blood vessels
Explanation:
Issun Sengeki... Messatsu!
Alike of what the other guy said, only the female mosquito sucks blood.
Being that this is true, the mosquito(s) could have been in any environment. They could carry diseases and illnesses. On top of that, they can carry microscopic organism, unlike diseases, that can cause infections.
