Decide Whether Integration by Parts or Substitution Should Be Used $\int$

Decide whether integration by parts or substitution should be used to compute the indefinite integral $\int$ $\frac { - \mathrm { e } ^ { 1 / \mathrm { x } } } { \mathrm { x } ^ { 2 } }$ dx If substitution, indicate the value of u; if by parts, indicate f(x) and g(x) .

A) substitution; u = $x ^ { - 2 }$
B) integration by parts; f(x) =- $\frac { 1 } { x ^ { 2 } }$ , g(x) = $e ^ { 1 / x }$
C) integration by parts; f(x) = - $e ^ { 1 / x }$ , g(x) = $\frac { 1 } { x ^ { 2 } }$
D) substitution; u = $\frac { 1 } { x }$
E) none of these
Evaluate the integral.