Shoppers in sporting goods stores, unlike in department stores, do very little impulse shopping, not buying a pair of skis and a boomerang when they come in for a basketball, but they leave with a basketball only.

A.those in department stores, do very little impulse shopping, do not buy a pair of skis and a boomerang when they come in for a basketball, but leave with only a basketball
B.those in department stores, do very little impulse shopping; someone who comes in for a basketball will leave with a basketball only and not buy a pair of skis and a boomerang as well

答案是B
  A哪里不对呢？