Ans.
Molecular biology can be defined as a branch of biology that includes study of molecular basis of cells, interaction between biomolecules, such as proteins, DNA, and RNA, their synthesis, functions, and regulation. Thus, it is correctly matches with 'DNA of a pig and a calf arrow.'
Comparative anatomy involves study of similarities and dissimilarities between the anatomy of organisms of different species. Thus, it is correctly matches with 'limb structure of a pig and a calf arrow.'
Development biology is a branch of biology, which concerns the growth and development of organisms. Thus, it is correctly matches with 'embryo of a pig and a calf.'