Final answer:
For a plant to produce diploid gametes, nondisjunction must occur during meiosis. It is an error that leads to gametes with an abnormal number of chromosomes that may produce a diploid offspring when fused.
Step-by-step explanation:
For a plant to produce diploid sperm and egg, nondisjunction must occur during meiosis. This can happen when chromosomes do not segregate properly during cell division. The correct answer to this question is c) Nondisjunction, meiosis. In normal meiotic events, cells are supposed to divide to form haploid gametes, which have half the number of chromosomes as compared to the diploid parent cells. Nondisjunction during meiosis can lead to gametes with an abnormal number of chromosomes (n+1 or n-1), and if two such gametes fuse during fertilization, they may produce a diploid or aneuploid offspring instead of the standard haploid product. Independent assortment, however, is an important feature of meiosis as well, which ensures genetic diversity by means of random assortment of chromosomes.