Select the Value(s)of W for Which $y = e ^ { w t }$

Select the value(s) of w for which $y = e ^ { w t }$ satisfies $\frac { d ^ { 2 } y } { d t ^ { 2 } } - 49 y = 0$ .

A) 7
B) -7
C) 49
D) -49
E) 0