The answer is: D.oxymoron.
The oxymoron is a combination of contradictory or incongruous words.
In this example, deafening silence.
Deafening is a noise so loud as to make it impossible to hear anything else.
Silence is oposite of deafening, complete absence of sound.
Other examples are: big baby, original copy, living dead, sweet sorrow, soft rock, pretty ugly.