The correct options are
A DNA undergoes changes in the germ cells of A and B
D Chromosome number changes in the germ cell of A and B
Speciation is the evolutionary process by which new biological species are formed. Speciation can take place if there are severe changes in DNA, e.g., changes in the chromosome number or genes. Due to which the germ cells of A and B might not be able to fuse with each other. This ultimately gives rise to new independent species.