一定质量的理想气体沿图示状态变化方向从状态a到状态b，到状态c再回到状态a．三个状态的体积分别为v_a、v_b、v_c，则它们的关系正确的是（   ）

俄罗斯的西伯利地区人口集中分布在南部，其主要的影响因素是（　　）

(____) I'm looking out of the window.

(____) Some children are making a snowman.

(____) In this photo，we are in the mountains.

(____) The wind is blowing and the sun is shining.

(____) I am having a lovely time.

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