Answer: Scarcity
Explanation:
Scarcity heuristic is the assigning value to the items or things based on difficulty of acquiring or getting it. If something is valued high , then it is supposed that it is not easy to get and if something is easily achieved, value is low.
According to the situation in question, shopping television channels put timer on the screen to states about the amount of time left for buying any item otherwise the item's stock will get over .This strategy creates pressure on the audience to buy the good before it gets out of stock.
If the timer wouldn't be set, audience will not value the product but along with timer it creates increase in value for the product that it will get stocked out if not bought on time.Thus ,scarcity heuristic is depicted from the situation.