Marx and Engels believed:
C) The proletariat would eventually own the means of production.
The errors of the other answers:
a) Marx and Engels believed that capitalists, owners of the wealth and in control of the state, would always create laws favoring their own interests. Eventually the lower classes would have to rise up against them if there was to be any change.
b) Marx himself didn't say much about imperialism, but later, Lenin wrote an essay titled, Imperialism: The Highest Stage of Capitalism (1917). Don't expect imperialists, who thrive on subjugating other peoples, to be abolishing any sort of class or privilege distinctions.
d) The bourgeoisie had risen up against the feudal system of aristocracy and had become the capitalist class. The next phase of revolution would be the proletariat (the workers) rising up against the bourgeoisie.