Let $B=\{a, b, c,\{d\},\{e, f\}\} .$ Answer each of the following as true or false.
$$
\begin{array}{ll}{\text { a. } a \in B} & {\text { b. }\{b, c, d\} \subset B \qquad \text { c. }\{d\} \in B} \\ {\text { d. }\{d\} \subseteq B} & {\text { e. }\{e, f\} \in B \qquad \text { f. }\{a,\{e, f\}\} \subset B} \\ {\text { g. }\{e, f\} \subset B}\end{array}
$$