I believe it the red blood cells
The correct answer is - A. Death rate.
We get the fertility rate from the birth rate and the death rate. More specifically, from the number of the children that are born in a given time frame (usually a year) we minus the number of the people that have died in the same time frame, so the difference between them gives us the fertility rate.
The fertility rate can be positive (in the difference is a positive number) and negative (if the difference is negative number).
Answer;
+1,-1,+2,-2,+3,-3
Explanation;
-Valence is the number of electrons lost or gained to complete an element's outer energy level.
-When an atom gains or loses a valence electron, it forms an ion. Atoms form ions in order to help another to obtain a full octet and to stabilize the valence.
-Some atoms gain or lose electrons to form ions because they need to become more stable. They sometimes give them to have an outer shell or gain them to get a closer charge to eight.
the answer to your question is d
Electron Transport chain, the final stage of cellular respiration