On the other hand typical human contains app. 50 trillion cells<span>
</span>
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.
Answer:
NK cells<em><u> perform all of these roles</u></em>
<em><u /></em>
hope this helps
-lvr
Recombinant DNA is the answer