The method that renders the seed coat permeable to water so that embryo expansion is not physically retarded, is
vernalisation
stratification
denudation
scarification
In many plants, the seed coats are quite tough and provide mechanical resistance to the growth of the embryos. Scarification done by abrasion through machine, threshing, filing, etc this process is done to rupture or weaken the seed coat and promote germination.
Hence, the correct answer is option 4.