To laughter and contempt; that she may feel

How sharper than a serpent's tooth it is
To have a thankless child! Away, away!

The dominant figure of speech in this passage is:
A) alliteration
B) assonance
C) simile
D) metaphor
E) imagery

And you think it's ... ?

I have a feeling it's either metaphor or alliteration, but I'm not sure.

Or maybe imagery?

If it's metaphor, what two things are being compared?

If it's alliteration, what consonant sound is being repeated?

"sharper than a serpent's…" repeats the 's' sound?

could be

What about any comparison?

For alliteration, the sounds are normally in the same place in the words. Here's an example of alliteration with r's:

" ... rifles' rapid rattle ... "

comparing the way he feels to being sharper than a serpent's tooth?

What is sharper than a serpent's tooth?

(This one is correct.)

Metaphor