Which structure is labeled x in the diagram below?
a. ribosome
b. lipid envelope
c. protein tail
d. capsid protein

Option D

Explanation:

Diagram is attached.

Capsid protein is a form of structural protein which usually forms part of a complex which later produces protective shell around the nucleic acid in a virus. It is also referred to as coat protein or head protein.  

Capsid acts as a distinguishing feature for identifying an integrated viral genome, plasmids and other genetic material of viruses. In fact, viruses are termed as organisms that encode capsid proteins.  

Hence, option D is correct

D. Capsid Protein

Explanation:

Just got it right on the quiz

answer: b

coz red blood cells marrow and circulates the body for 120 days.