"tone" refers to
the attitude of the speaker
the mood of the audience
the main idea of the passage
the stage directions of a play

Answer;
Tone refers to the attitude of the speaker; 

Explanation;
The tone of a poem makes the attitude the poem takes, towards its subject and theme, clear. one can refer the attitude as the feeling or disposition that is presented in a given poem.
Mood on the other  hand is the feeling or atmosphere by the audience. 

"Tone" refers to the attitude of the speaker. The correct option among all the options that are given in the question is the first option. the other choices are incorrect and can be avoided. I hope that this is the answer that you were looking for and this is the answer that has come to your desired help.