Ans.
New combinations in gametes can produce by errors, during meiosis or by crossing over during meiosis as gamete formation (formation of sperms and eggs) occurs through meiosis. Mutations in germ cells also lead to production of new combinations as mutations are heritable changes.
Mitosis is a type of cell division that takes in normal body cells or somatic cells of eukaryotic organisms. Hence, errors during mitosis cannot produce gametes with new genetic combinations.
Thus, the correct answer is option B). 'errors during mitosis.'