Adding organic material such as compost to soil can also make lead less available to plants.

VOA: special.2009.06.09

Everything is interconnected on the higher level on a spiral-- in other words will lead to deep understanding and hopefully assimilation of the material.

所有内容在一个更高的水平上呈螺旋状互相联系-,换言之，会带来深刻的理解和我所希望的对材料的吸收。

哈佛公开课 - 幸福课课程节选