(d) Surgical methods
Explanation:
Surgical methods of contraception like tubal ligation for women and vasectomy for men involve medical procedures that are invasive and often irreversible. These procedures are designed to permanently prevent pregnancy by blocking or severing the reproductive pathways. In contrast, the other options listed - natural methods (like fertility awareness), barrier methods (like condoms), and oral methods (like contraceptive pills) are non-invasive and often reversible forms of contraception.