Final answer:
In Brutus's soliloquy from Shakespeare's 'Julius Caesar', the rhetorical device used is metaphor, likening Caesar to a venomous snake that might become dangerous if given more power, which corresponds to answer choice D.
Step-by-step explanation:
The rhetorical device that Shakespeare uses in the given section of Brutus's soliloquy ("It is the bright day that brings forth the adder, And that craves wary walking. Crown him that, And then I grant we put a sting in him, That at his will he may do danger with. Th' abuse of greatness is when it disjoins Remorse from power.") from Julius Caesar is metaphor. In this soliloquy, Brutus compares Caesar to a venomous snake or adder which becomes more active and poses a greater threat on a sunny day. The metaphor implies that just as snakes can be more dangerous when they are out in the open, so too could Caesar become more dangerous if given more power. Answer choice D is the correct one as it states that the venomous snake is a metaphor for Caesar's potential nature should he become king.