A beggar wrapped himself with a few layers of newspaper on a cold winter night. This helped him to keep himself warm because
$(a)$. friction between the layers of newspaper produces heat.
$(b)$. air trapped between the layers of newspaper is a bad conductor of heat.
$(c)$. newspaper is a conductor of heat.
$(d)$. newspaper is at a higher temperature than the temperature of the surrounding.

So, option $(b)$ is correct.