$\text { Which of the following is a solution of the differential equation } 7 y ^ { \prime \prime } + 7 y = 0 \text { ? }$

$\text { Which of the following is a solution of the differential equation } 7 y ^ { \prime \prime } + 7 y = 0 \text { ? }$

A) $x ^ { 2 } e ^ { x } - 3 x ^ { 2 }$
B) $C _ { 1 } e ^ { - x } \cos x + C _ { 2 } e ^ { - x } \sin x$
C) $- \cos x \ln | \sec x + \tan x |$
D) $C _ { 1 } \cos x + C _ { 2 } \sin x$
E) $e ^ { - 3 x } + e ^ { x }$