Class Activity: Sets and Subsets

This is a graded class activity and is supposed to be completed in 15 minutes.

Consider the following sets:

$A=\left\lbrace a,b,c,d\right\rbrace$

$B=\left\lbrace b,c\right\rbrace$

$C=\left\lbrace\left\lbrace a,b\right\rbrace,\left\lbrace c\right\rbrace\right\rbrace$

a) Write down all the subsets of $B$

b) Write down all the subsets of $C$

c) Which one is a subset of $A$? $B$ or $C$?