How does protochlorophyll differ from chlorophyll due to the lack of which component?

• A
  Lack of $2$ hydrogen atoms in $1$ pyrrole ring.
• B
  Lack of $2$ hydrogen atoms in $2$ pyrrole rings.
• C
  Lack of $4$ hydrogen atoms in $1$ pyrrole ring.
• D
  Lack of $4$ hydrogen atoms in $2$ pyrrole rings.