3-4 What is biodiversity and why is it important?

3-4-science forcus-第6段

The space,or pores,between the solid organic and inorganic particles in the upper and lower soil layers contain varying amounts of air (mostly nitrogen and oxygen gas) and water . plant roots use the oxygen for cellular respiration . as long as the O and A horizons are anchored by vegetation,the soil layers as a whole act as a sponge,storing water and releasing it in a nourishing trickle.

空間，或毛孔之間土壤的有機和無機粒子上部和下部土層含有不同數量的空氣（主要是氮和氧氣）和水。利用植物根系的氧氣供细胞呼吸。只要在O和A層土壤被植被的根細繫住，土壤層就像一個整體作為一個海绵，儲存和釋放水的細微養分。


重點:
說明植物根系下土壤裡含有的養分及功能(土壤空隙中含有氮氣跟氧氣以及有機和無機的粒子跟水分)


題目:
植物根系下的土壤就像一個海綿體，能夠吸收並且釋放養分，藉此供給植物利用，而植物的根系主要是介於哪兩個土層利用這些養分??(A)O和A(B)A和B(C)O和C(D)B和C。