Draw a single lewis structure for the phosphate ion (po43−), assuming that the phosphorus atom can expand its octet such that the formal charge on each of the atoms is minimized. include all formal charges and lone-pair electrons.

The Lewis diagram with single bonds, and all the oxygens have 3 lone pairs.  PO4^3- has 5+4x6+3 = 32 e-

.. O 

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O-P-O 

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...O 

The only purpose that you might want to contain a double bond is for the reason that of an excessively strict adherence to formal charges. By creating one of the bonds a double bond you decrease the formal charge on P from +2 to +1 and one of the oxygens from -1 to 0. 

The detail is that all four bonds are undistinguishable. If one of the bonds was a double bond then one bond would have a superior energy that the others. That is why you could use resonance, to make all the bonds equal.

The answer is D, they help the patient giving the proper amount of nutrients. Come on bro, don't tell me your actually using for this question.

Explanation:

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