Which of the Following Principles of Darwin's Theory Were Guided

Which of the following principles of Darwin's theory were guided by his reading of the economist Thomas Malthus?

A) The world is old.
B) Individuals resemble their parents.
C) There must be checks on survival and reproduction in nature, or else the world would become overcrowded.
D) Like compound interest, small successive changes in a trait each generation can lead to the large differences that we see between species.
E) Nature acts like the breeders of pigeon, selecting the traits most useful to the organism.