Because the vaccinations are producted in HK or Shanghai...
The answer is b. I am not sure exactly how to explain this, but it fits in much better with that question. I hope this could help you!
<h2>Ur Answer:-</h2>
The cambial ring becomes active and starts cutting off new cells; both on the inner and the outer sides. The cells which are cut off towards the pith mature into secondary xylem. The cells which are cut off towards the periphery mature into secondary phloem.
<h2>Hope it helps uh!</h2>
