题目

The ________expression on his face suggested that he was ________what he had seen. A . amazed; amazing B . amazed; amazed C . amazing; amazed D . amazing; amazing 答案：B在试管牛的生产过程中，不是必需的操作是A．核移植技术B．卵母细胞的采集和培养C．精子的采集和获能D．早期胚胎培养和胚胎移植