什么是有效氮、有效磷?
参考答案:
有效氮:NH4+、NO3-、NO2-;有效磷:溶解的无机磷酸盐,这部分称为有效磷,PO43-(少量)、HPO42-、H2PO4-。
He was admitted to a famous university,________ was obvious that his situation had gone beyond his parents’ expectations.
A.what
B.it
C.as
D.and it