The correct answer would be d. Finches looked alike, but ate different things.
Darwin observed that the finches looked alike, however, they had evolved different traits like body size, different shape and size of beaks due to different eating habits.
For example, finches which used to feed on seed used to have short and stouter beaks whereas the finches which used to feed on insects used to have sharp and cylindrical beaks et cetera.
the process by which different kinds of living organisms are thought to have developed and diversified from earlier forms during the history of the earth.