可以在候选人之间形成相应的竞争，为选民行使选举权提供选择余地的选举方式是（  ）

根据短文内容，选择最佳答案。
B
    Hello! My name is Kate. This is my bag. It's a nice bag, right? It is from my mother.
    What's in my bag? A ruler is in it. And the ruler is white. It's not mine. It's Lily's. Lily is my sister. She likes white but I don't. Two pencils are in it, too. One is red and the other is blue. They are mine. Look, a nice watch is in it. The watch is white and blue. It's mine and it's from my father. A notebook is in my bag, too. The notebook is yellow and blue. Is this notebook mine? No, it's Anna's. Anna is my cousin. She likes yellow and blue very much.

关于我国气温和降水的说法正确的是（　　）

有A,B,C,D四种物质，A是无色无味气体，B在A中可以剧烈燃烧，产生明亮的蓝紫色火焰，且生成有刺激性气味的气体C，将燃着的木条伸入无色无味的气体D中，木条熄灭，向D中加澄清石灰水并振荡，石灰水变浑浊，请用化学式表示A,B,C,D各是什么物质．

A是____；B是____；C是____；D是____．

某射击运动员练习射击，5次成绩分别是：8、9、7、8、x（单位：环）．下列说法中正确的是（　　）