You've forgotten to attach the thing you need help with.
Answer:
Leukocytes are also called white blood cells. These cells have a nucleus, unlike red blood cells that lack a nucleus. Also unlike red blood cells, white blood cells do not contain hemoglobin, which means they're not involved in the transport of oxygen.
it is Adaptations i think
A reverse reaction is the chemical reaction moving both forward and backwards.
An example of this is Ammonium chloride ⇌ ammonia + hydrogen chloride
This is a symbol for reverse reaction ⇌