When a salesperson visits your home and asks you to try a free sample of a cleaning fluid, you agree. When he returns the following week and asks you to purchase an assortment of expensive cleaning products, you make the purchase. The salesperson appears to have made effective use of:

The answer is the foot-in-the-door phenomenon.

Explanation:

This persuasion technique consists in asking for a small request, followed by a larger one that will likely be accepted. This can be explained because the person requested feels socially responsible for complying after a smaller favour has been already accepted.

Naturally, this technique is extensively used in marketing. In fact, the name itself refers to a salesperson placing his foot on the door to prevent it from closing.

the 4th option is the answer

i dont know sorry why dont you looking it up on google