Which of the following scenarios best describes herd mentality?

a) Heather inherits money from her grandfather and places it in a savings account rather than the stock market.
b) Jennifer spends the majority of her paycheck on a popular pair of shoes that her friends wear.
c) Brittany purchases one more item on an online store in order to receive free shipping.
d) Rachel applies for a store credit card at the register to get 30% off her purchase and earn bonus points on future purchases.