<span>Mammal is your answer hope this helps
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The series explores strategies to sustainably feed more than 9 billion people by 2050. All pieces are based on research being conducted for the 2013-2014 World Resources Report. The world is projected to hold a whopping 9.6 billion people by 2050.
I believe it is A because Living things respond to changes, each and every living organism is made up of cell and adapting to changes is same as responding to changes.So, only one left is A.
It is Gravity.
Hope this helps.