It Was Sunny When Jenny Went to Class, but by the Time

It was sunny when Jenny went to class, but by the time class was over it was raining heavily, so Jenny stopped by the student store to buy an umbrella before she walked back to her dorm. In this case, the umbrella is an example of a(n) ________.

A) impulse good
B) specialty good
C) homogeneous shopping good
D) emergency good
E) heterogeneous shopping good