Cho sơ đồ chuyển hóa sau:
(1) ${{C}_{4}}{{H}_{6}}{{O}_{2}}\text{ }\left( M \right)+NaOH\xrightarrow[{}]{{}}\left( A \right)+\left( B \right)$
(2) $\left( B \right)+AgN{{O}_{3}}+N{{H}_{3}}+{{H}_{2}}O\xrightarrow[{}]{{}}\left( F \right)+Ag\downarrow +N{{H}_{4}}N{{O}_{3}}$
(3) $\left( F \right)+NaOH\xrightarrow[{}]{{}}\left( A \right)+N{{H}_{3}}\uparrow +{{H}_{2}}O$
Chất M là
Gợi ý câu trả lời: