Use the Process of Factoring by Grouping to Factor the Polynomial

Multiple Choice

Use the process of factoring by grouping to factor the polynomial. $p ^ { 2 } - 7 p - 3 p + 21$

A) $( p - 3 ) ( p - 7 )$
B) $( p + 3 ) ( p - 21 )$
C) $( p - 3 ) ( p + 7 )$