The correct answer is answer D "deadly".
The word wanton refers to a deliberate, malicious or violent action which can very easily be read as deadly or associated with such attribute, specially in the context of the poem.
In "The Nymph's Reply to the Shepherd", death is one of the biggest themes. When the nymph sees the shepherds gifts, she can't help but acknowledge that anything that has mortality eventually rots and ends.
Hope this helps!