A Thermo Keeps a Hot Drink Hot and a Cold

Multiple Choice

A thermo keeps a hot drink hot and a cold drink cold for a long time.Shown below is a cut-away section of a thermo with the important features labeled.The reason for the silvered double-wall vacuum chamber is

A) the silvered surfaces reflect any radiation while the vacuum suppresses heat losses by convection and heat conductivity.
B) people like silvery thing so it is a marketing tool.The vacuum keeps the container clean.
C) the silvered surfaces suppresses heat conduction and convection and the vacuum prevents radiated heat.
D) because putting silvery surface is easy to manufacture,and while they are at it,might as well put a vacuum in between.
E) none of the above