Option 1 indicates that global warming might trigger the release of methane gas from these deposits and large deposits of ‘methane hydrate’ are found in Arctic Tundra and under the seafloor. Both of these statements are accurate, as increased temperatures from global warming can destabilize methane hydrates and cause them to release methane gas. Further, large methane hydrate deposits are indeed located in these cold or deep regions.

Option 2 suggests that large deposits of ‘methane hydrate’ are found in Arctic Tundra and under the seafloor, and that methane in the atmosphere oxidizes to CO2 after a decade or two. Both these statements are correct. The first one has already been explained making the second clear - methane converts into CO2 over time, but the process is much prolonged between a decade or two.

Option 3 states that global warming might trigger the release of methane gas from these deposits, and that methane in the atmosphere oxidizes to CO2 after a decade or two. Both are true - methane release due to global warming is feared for its potent greenhouse effects, one of those effects being its eventual oxidation into CO2.

However, the answer is Option 4 as all statements are correct, as noted above.