Hello!
The correct answer to this question is C: rate.
Volume simply means how loud your voice is, but it does not mean that you are speaking too quickly. Pitch means the sound of your voice. For example, if you talk in a very squeaky voice, you are said to be speaking with a high pitch. Tone means the way that you are speaking. When you are happy and you speak excitedly, or angry and you speak as if you are annoyed, these are examples of tone.
I hope this helps answer your question!