【单选题】传统的动物资源保护措施主要是划定保护区或建立保种基础。这些措施能很好地保护物种的多样性,但也存在一些缺点:保护区面积大,偷猎现象屡禁不止;建立良种基地保护地方品种投资大,时间长,容易出现近亲繁殖、物种衰退等现象。试管、克隆、冷冻保存等生物技术新成果的问世,为动物遗传资源的保护和利用开辟了新途径,建造“动物诺亚方舟”不再是天方夜谭。 这段文字主要介绍了()
【单选题】Since the September 11 attack, US President George W. Bush has 【21】______ himself as a superpower leader of hard resolve, tolerating no 【22】______ to his goals-until he came up against Israel. 【23】___...
【单选题】要使某图层与其下面的图层合并并可按( )快捷键。
【单选题】How ________the woman is to save the boy from the danger of earthquake.
【单选题】听力原文: US President George W. Bush said that the United States will help train a new Afghan military but made clear he would not commit US troops to peacekeeping. He made the remark yesterday when meet...
A.
provide a British-led force with information and materials.
B.
help a British-led armed force in military training.
C.
help to train new soldiers only in a. British-led force.
D.
provide the new Afghan army with military information.
【单选题】It was() late to save the drowning boy as he had gone down for the third time.
【单选题】The passer-by jumped into the cold water to save the _____ boy, who cried for help, but it was too late and the boy was _______ at last.
【单选题】在下面一段话的空缺处依次填入词语,最恰当的一组是 ( ) 中国文学具有源远流长、 ▲ 的特点。若论文学的悠久,只有古希腊文学、古印度文学可以与中国文学比肩;若论文学传统的绵延不断,任何别的国家和民族的文学都不能与中国文学 ▲ 。中国文学一直以丰富的作品、持久的魅力 ▲ 着全世界。
【单选题】下列激素中,可直接促进肾远曲小管和集合管重吸收Na+的是()
【单选题】I don’t know how they ____the first couple of weeks after the strong earthquake.