It's like that old chicken and egg question—which came first? How fashion in American culture is determined has puzzled social scientists for years. Think about it: An ad comes on TV showing a bunch of teenagers all happily wearing a stylish new pair of designer jeans. You think to yourself, "Hey, that must be what all my friends will be wearing this coming year, so I better go get some!" You just know you'll be the laughing stock of the school if you aren't wearing those jeans. But how did the clothing maker decide to make this style of jeans? Did company representatives go out and survey teenagers, showing them a bunch of designs and asking which they liked? Or did the maker just decide on a fashion, and have its ad writers sell the idea to teens, convincing them that this is the "in" thing to wear? Over the past decades, TV commercials for jeans have changed as the fashions shifted. There were bell bottoms in the seventies; straight-leg jeans in the late eighties and nineties; and now the ads all show hip-huggers for girls, and baggy, low-riding jeans for boys. Did the public simply decide it was ready for a change, and the fashion industry responded? I don't think so. I'm here to tell you the clothing manufacturers dictate the styles, not our changing tastes.
My reasoning is simple: It's in the companies' best interests to change clothing styles often. If the same style stays in fashion, there would be no reason for us to buy different clothes until our old ones wear out! And if we didn't buy fashionable new clothes, the companies wouldn't make their money. Go ahead—look in your closet. I'll bet you have clothes you don't wear anymore just because they've gone out of fashion, even though they're perfectly good still. Also, in order to stay competitive, clothing makers have to change styles as a way of saying, "We're coolest and hippest, and we're not like those other companies." It distinguishes one manufacturer from another. From Guess Jeans to Levis 501's, companies compete for whose fashion will catch on and make a fortune.
The only way to shift the tide and not let the clothing manufacturers have so much power is to flat out rebel. We'd have to decide that being "in fashion"—wearing the same sort of thing as everyone else—is just not that important. Being that the teenage years are all about fitting in and not sticking out, I don't see that happening anytime soon, do you?

Question: In the last paragraph, what does the author mean by the phrase, "shift the tide"?
a
alter how fashion is currently decided
b
change from one fashion to another
c
wear the same clothes as everyone else
d
get the oceans to behave differently