Use $\subseteq, \nsubseteq, \subset$ , or Both $\subset$

Multiple Choice

Use $\subseteq, \nsubseteq, \subset$ , or both $\subset$ and $\subseteq$ to make a true statement.
- $\{ \mathrm { s } , \mathrm { r } , \mathrm { t } \} ........ \{ \mathrm { s } , \mathrm { r } , \mathrm { t } \}$

A) $\subseteq$ and $\subset$
B) $\subset$
C) $\nsubseteq$
D) $\subseteq$