The correct answer is (d). Given that CH4 emissions from enteric fermentation was a key category for all Annex I Parties, all Parties should use a Tier 2 method (or equivalent) and, to the extent possible, country-specific emission factors. Austria and New Zealand reported to have used a Tier 2 method with country-specific emission factors for all significant sub-categories. They have reported using a Tier 1 method with default emission factors for other non-significant sub-categories and have provided justifications for their use. Slovakia, however, reported that it used a Tier 1 method and default emission factors.