题目

阅读理解Aliving robot has been created out of frog skin cells. Xenobots, named after thefrog species Xenopus laevis that the cells come from, were first described lastyear. Now the team behind the robots has improved their design and demonstratednew capabilities.Tocreate the xenobots, Michael Levin at Tufts University in Massachusetts and hiscolleagues obtained tissue from 24-hour-old frog embryos after very smallphysical operation. Where the previous version relied on the contraction ofheart muscle cells to move them forward by pushing off surfaces, these newxenobots swim around faster. T33、下图，a、b、c、d分别表示四个国家。读图完成下列要求： （1）四国中属于发达国家的是       (填名称)。我国从      、      、      等所示国(用图中字母表示)进口铁矿石。 （2）b和d所示国家都盛产的重要经济作物是      ，适宜该经济作物生长的自然条件是                        。 （3）a和c所示国家的城市相对集中分布于东南沿海地区，其共同区位因素是            。