一朵花中主要部分是____和____,因为这两种结构可分别产生____和____。
下列选项中,哪一项与生物圈中碳氧平衡没有直接关系?( )
阅读下列短文,从每小题的三个选项中选出最佳答案
It is morning now. Look at the sun, it rises in the east(东方). Look at the tree, the shadow is long. It is noon now. The sun is high in the sky. It is very hot. Look at the tree. The shadow is short. It is evening now. The sun goes down in the west(西方). Look at the tree, the shadow is long again. It is night now. The moon is high in the sky. There are some stars in the sky too.
美国首先提出建立国际联盟,后来却没有参加,原因是( )①英法等国和美国有矛盾②美国国内的阶级矛盾空前尖锐③国联盟约未能满足美国的要求④盟约否定了十四点和平计划
选出下列划线的词语注音全正确的一组( )