The author explains the trend of gift-giving on the occasion of holidays, birthdays, anniversaries, weddings, graduations and baby showers. The answer to the question lies in line 28-30.
People tend to buy gifts that recipients would not choose to buy on their own, or at least not spend as much money to purchase. This phenomenon is referred to as 'the deadweight loss'. This phenomenon is described as predictable as gift-givers are not very good at predicting what gifts others will appreciate.
Also, it is itself not surprising to social psychologists.
Thus, option A is the correct answer. Rest of the options are wrong.