Cho sơ đồ chuyển hóa : P2O5 + KOH ra X + H2PO4 ra Y + KOH ra Z Các chất X, Y

A. ${\mathrm{K}}_3{\mathrm{PO}}_4, {\mathrm{K}}_2{\mathrm{HPO}}_4, {\mathrm{KH}}_2{\mathrm{PO}}_4$

B. ${\mathrm{KH}}_2{\mathrm{PO}}_4, {\mathrm{K}}_2{\mathrm{HPO}}_4, {\mathrm{K}}_3{\mathrm{PO}}_4$

C. ${\mathrm{K}}_3{\mathrm{PO}}_4, {\mathrm{KH}}_2{\mathrm{PO}}_4, {\mathrm{K}}_2{\mathrm{HPO}}_4$

D. ${\mathrm{KH}}_2{\mathrm{PO}}_4, {\mathrm{K}}_3{\mathrm{PO}}_4, {\mathrm{K}}_2{\mathrm{HPO}}_4$