Which of these events is the best example of salutary neglect? An untended garden becomes tangled with weeds. An untended garden grows and blooms. An untended garden withers and dies.

The answer is: An untended garden grows and blooms.

A salutary neglect can be understood as a form of not giving enough attention nor caring for the needs of someone or something and, still, getting good and beneficial results. Which is what the sentence expresses:

"An untended garden" = neglected.

"Grows and blooms" = Good results despite neglection.