Given Are the First Three Terms of a Sequence That $9,13,17$

Multiple Choice

Given are the first three terms of a sequence that is arithmetic. Find a1 and d.
- $9,13,17$

A) $a _ { 1 } = 9 ; d = 12$
B) $a _ { 1 } = 9 ; d = 9$
C) $a _ { 1 } = 9 ; d = 4$
D) $a _ { 1 } = 9 ; d = 3$