Which of the Following Is the Correct Definition of Piloerection

Which of the following is the correct definition of piloerection?

A) When the penis becomes erect prior to sexual intercourse
B) When the taste buds in the tongue pop out, in response to food or irritation
C) When the small hairs in the ears are activated by sound
D) When muscles around hair follicles contract, so the hair stands up on end