Which is not an advertising technique ?
a. image appeal
b. bandwagon
c. celebrity endorsement
d. pleading

Pleading is not an advertising technique. It is simply an act of causing a passionate or serious appeal to someone. Whereas, advertising appeals are intended to build an assertive image and mindset of those who utilize the product or service and are an important circumstance of concern for merchants. Similarly, Bandwagon advertising is a particular type of publication promoting technique that attempts to perceive the objective public to jump on board, so as to not "miss out" on what everyone else is performing. And celebrity endorsement is a kind of promotion operations or marketing approach adopted by trademarks, corporations, or a non-profit group which includes celebrities or a well-known person.

i've never heard of it before.