题目

我国栽培的小麦、大豆，每种中都有十分丰富的品种资源，这能说明（   ）     A．生物种类的多样性    B．基因的多样性     C．生态系统的多样性    D．基因控制性状 答案：BI can't believe that great changes_______ in Suzhou in the past 20 years.A．has been taken placeB．have taken placeC．took placeD．have been taken place