【单选题】—Are you worried when your son often plays computer games? —Yes. I think playing too many computer games ______ on teenagers. [ ]
【单选题】右图是物种形成的一种模式。物种a因为地理障碍分隔为两个种群a1和a2,经过漫长的进化,分别形成新物种b和c。在此过程中某一时刻,a1种群的部分群体越过障碍外迁与a2同域分布,向d方向进化。下列有关叙述正确的是()
C.
a1中的外迁群体与当时留居群体的基因频率相同,则b和d是同一物种
D.
a1中的外迁群体与当时a2种群的基因频率不同,则c和d是不同物种
【单选题】I think playing ______ football is a good way to learn the spirit of teamwork.
【简答题】I think playing football is _______than _________ TV. A healthier , watching B. healthier ,watch C .more healthy, watching D. more healthy , watch.
【单选题】I think playing table-tennis is a____________sport.