The correct option is
C Mob
The given word 'rabble' means 'a disorderly crowd or a mob'.From the options, Option A: 'mob' best expresses the meaning of the given word. Hence option A is correct.
Option B: 'Noise' is a harsh, loud sound of a confused kind.
Option C: 'Roar' means 'utter a loud, deep cry'.
Option D: 'Rubbish' is something that is worthless or unwanted.
These words do not mean the same as the given word, hence options B, C and D are incorrect.