I think there are a couple of advertising techniques being used in this ad. First there is the “bandwagon” technique. This technique uses the idea that everyone wants to be on the winning side and be like the rest of the crowd, that is, be popular. By using the deodorant, the girl will be jumping on the bandwagon, becoming like everyone else (no body odor) and becoming popular. You see this a lot with clothing ads.
Another technique that seems to be used is the idea of simple solutions. Relationships between boyfriend and girlfriend are complex things. Here, the solution to any boyfriend/girlfriend problems is simple--smelling good by using the advertised deodorant. Make-up ads are good at this, too. Use a certain kind of make-up and all your problems will be solved because you will look good.
One of the main things that advertisers have been doing (at least in the United States) since the 1920s is to make ads like this one. These ads play on the fact that people tend to be afraid that they will not fit in and will be rejected by society. I imagine your textbook or teacher has a specific name for this -- I would call it the motive of fear of rejection.
Many ads have this sort of a theme. They try to tell you that no one will want to be around you if you do not use their product or that you will in some way be deficient. This is especially true about products having to do with your body. You see this in many deodorant ads. Here in the US the Sure brand of deodorant had a campaign "Raise your hand if you're Sure" where people who used the deodorant were willing to raise their hands but others were afraid to because they did not want to expose smelly and wet underarms. You can see this sort of thing also in ads for weight loss products.