How did marx's "scientific" brand of socialism differ from utopian or practical socialists?

a. marx did not believe that socialism was practical or utopian, but instead that it was dangerous.
b. marx felt that socialism would only be possible if it was achieved through agreements with capitalists in power.
c. marx realized that it was scientifically impossible for the government to take ownership of the means of production and means of distribution.
d. marx had a more scientific theory as to how socialism could be enacted, which was not dependent on appealing to the capitalists in power.