Factor the Trinomial, If Possible $$8 a ^ { 2 } + 21 a - 9$$

Multiple Choice

Factor the trinomial, if possible. $$8 a ^ { 2 } + 21 a - 9$$

A) $( 8 a + 3 ) ( a - 3 )$
B) $( 8 a + 3 ) ( a - 4 )$
C) $( 8 a + 3 ) ( a - 5 )$
D) $( 8 a - 3 ) ( a + 3 )$
E) prime