The red blood cells able to move through narrow vessels to carry oxygen throughout a multicellular organism because they are small because they lack a nucleus. Option D
The red blood cells are the ones that carry hemoglobin that is responsible for the transport of oxygen in the body. Now we know that the blood is responsible for the supply of oxygen across the body and this is why the red blood cells are important.
Thus, the red blood cells able to move through narrow vessels to carry oxygen throughout a multicellular organism because they are small because they lack a nucleus.
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