正确：The salesman spoke loudly, swayed back and forth, and tapped the table nervously, mannerisms which made his customers extremely nervous.
错误：It is difficult to distinguish between the scent of roses and that of tulips.
正确：T o distinguish between the scent of roses and that of tulips is difficult.
错误：His superiors have been following his progress. Some are more impressed than others. None are overwhelmed.