what is the difference between roaring and shouting?

I don't like our Chemistry teacher because he's always ......... at us.
(a) shouting
(b) roaring
(c) talking
(d) voicing
Correct answer: (a) shouting

Roaring is louder and deeper than shouting. Lions roar, for example. Or you can roar of laughter. Roaring can also refer to the sound of a volcano, a waterfall, a plane, a motorbike, the wind, the sea, fire, traffic, etc. 
Further examples: 
- the crowd roared its approval/delight/admiration
- she roared of laughter

what is the difference between roaring and shouting?

I don't like our Chemistry teacher because he's always ......... at us.
(a) shouting
(b) roaring
(c) talking
(d) voicing
Correct answer: (a) shouting

Roaring is louder and deeper than shouting. Lions roar, for example. Or you can roar of laughter. Roaring can also refer to the sound of a volcano, a waterfall, a plane, a motorbike, the wind, the sea, fire, traffic, etc. 
Further examples: 
- the crowd roared its approval/delight/admiration
- she roared of laughter