Answer:
B, phosphoric acid.
Explanation:
PO4 is a polyatomic ion. A isn't correct because polyatomic ions that contain an oxygen (O) atom never start with "hydro-" in it's acid form. C isn't correct because PO4 is phosphate, and polyatomic ions that end in "-ate" always end in "-ic" in it's acid (aqueous) form. D isn't correct because the question is asking for the molecule's name in it's acid form.
