下面是长沙岳麓书院的一副对联，为上联“地接衡湘，大泽深山龙虎气”选择下联，最合适的一项是（      ）

①水的质量m_水。

②A容器对水平桌面的压强p_A。

③若在两个容器中抽出相同深度的液体△h后，两容器中液体对底部的压强相等，请计算出△h的大小。

    This is a picture of Mr. Li's family. The man in the middle is Mr. Li. The woman is Mr. Li's wife. They have two sons. The child behind Mr.Li is Li Lei. He's thirteen. The other in front of Mrs. Li is Li Ming. He is eleven. Li Lei and Li Ming are in the same school, but not in the same grade. Li Lei is in Grade Two. Li Ming is in Grade One. They are good students.

1980年著名作曲家施光南深入安徽、四川农村体验生活，满怀激情地谱写了经典歌曲《在希望的田野上》。他选择赴上述农村体验生活的最主要原因是（    ）