One of the reasons why our sales team has become a leader today is that they are put through a number of vigorous training sessions to keep up with the ______ changes that occur in the market.
 
【正确答案】 B
【答案解析】 本题需选择符合句意的形容词。将备选答案一一代入后分析全句，“为了跟上市场的不断变化”最恰当，故本题选B。