控制细菌遗传、生长发育与代谢的结构是
A．性菌毛
B．质粒
C．鞭毛
D．中介体
E．核质
参考答案：E
—Are there any boats in the river?
—No, _____.[ ]
A. there isn't
B. there are
C. there is
D. there aren't
老年人蛛网膜下隙出血的特点为（）。
A.脑膜刺激征明显
B.常伴癫痫发作
C.头痛、呕吐严重
D.常伴眼底视网膜出血
E.头痛不明显，意识障碍多见
