Hi,
For A: 2 amine groups have gained a hydrogen, but only one hydrogen has been lost from the COOH group. Overall, there are more hydrogens gained than lost, so this answer is incorrect.
For B: 2 hydrogens lost from COOH groups, but only one hydrogen gained on the amine group. There are more hydrogens lost than gained, so it can't be this answer.
For C: Zwitterions are when the COOH group has donated a hydrogen to the amine group - for this structure, a hydrogen has been donated to the alcohol group, which does not meet the definition of a zwitterion, so this structure is incorrect.
For D: this answer is correct, as the number of hydrogens gained and lost adds up to 0, and there has only be hydrogens gained/lost between the amine and COOH group.
Hope this helps!