Find the Indicated Term or Coefficient of the Binomial Expansion $( s - t ) ^ { 6 }$

Multiple Choice

Find the indicated term or coefficient of the binomial expansion.
-Find the 4 th term of the expansion of $( s - t ) ^ { 6 }$ .

A) $- 20 \mathrm {~s} ^ { 3 } \mathrm { t } ^ { 3 }$
B) $s ^ { 2 } t ^ { 4 }$
C) $- s ^ { 3 } t ^ { 3 }$
D) $15 s ^ { 2 } t ^ { 4 }$