题目

________in gardening and volunteering work, Mrs. Black leads a busy and rich life at her old age. A . Employing  B . Employed C . To employ D . Being employed 答案：B（2010徐州） 人们获得“人工种子”所利用的生物技术是A．转基因技术B．组织培养技术C．动物克隆技术D．嫁接技术