台湾岛修建环岛铁路，没有直接联系东、西部的横向铁路，这样选择线路主要是考虑了哪种因素对铁路建设的影响（   ）

1921年3月俄共（布）通过如下决议：“纳税后剩余的一切粮食、原料和饲料，农民可以自己全权处理，可以用来改善和巩固自己的经济，也可以用来提高个人的消费，用来交换工业品、手工业品和农产品。”这表明苏俄将

图为叶片结构示意图，下列对相关结构和功能叙述不正确的是(     )

水有三态，其他物质是否也有三态呢？如果有，请你举出一例加以说明．

阅读短文，从方框中选择单词，根据实际情况用适当的形式，使短文意思完整、通顺。每空一词，每词只能用一次。

swim,  four,  snow,  after,  weather

    We know that there are ____ seasons（季节）in a year: spring, summer, autumn and winter. In spring, the ____ is warm. Everything grows fast. It is a good season for hiking (远足). Summer comes ____ spring. It is usually hot in summer. The children like to go ____. They are very happy in the cool water. It often rains and sometimes it rains heavily. In autumn, it is cool. The farmers are busy. It is often cold in winter. Sometimes it ____, and all the houses, trees and other things become white. The world is so beautiful in this season and people are very happy!