题目

短文填空 用下面方框中单词或词组的适当形式填空，使短文意思正确、通顺(每词限用一次)。they，build，great，place，park，interest，visit，one，because of，come Melbourne is in Australia．It is a beautiful city with huge gardens，great_______and many amazing buildings．Many people come to________it every year． Melbourne is also an ancient city in Australia．It has a(n)________history of more than 170 years．The________people came in 1835，and in the 1850s，gold was discovered．________this，Melbourne became a very rich city．Many new______生物的某些变异可通过细胞分裂某一时期染色体的行为来识别．甲、乙两模式图分别表示细胞分裂过程中出现的“环形圈”、“十字形结构”现象，图中字母表示染色体上的基因．下列有关叙述正确的是（　　） A、缺失和易位可以分别导致图中甲、乙所示现象的出现B、甲图是个别碱基对的增添或缺失，导致染色体上基因数目改变的结果C、乙图是四分体时期同源染色体非姐妹染色单体之间发生交叉互换的结果D、甲、乙丙图常出现在有丝分裂前期，染色体数与DNA数之比为1：2