Let A $=$ c$,$ d$,$ f$,$ gJ$,$ B $=$ t$,$ js$,$ and C $=$ d$,$ g$\}.$ Answer each of the following questions. Give reasons for your answers.

a$.$ Is B S A$?$

b$.$ Is C sA$?$

b$.$ Is C S C$?$

d$.$ Is C a proper subset of A$?$